BOB

The B.O.B is a special type of enemy encountered in Halo: Reach. The B.O.B.s usually take the form of gold-armored Sangheili Rangers. In the ONI: Sword Base level, B.O.Bs take the form of a white-armored Elite with randomly generated armor, ranging from Minor to Field Marshall. It is also possible for B.O.B.s to use Armor Lock.

Description
You do receive a medal for killing a B.O.B. However, the medal can only be viewed on Bungie.net. In the post-game carnage report, the B.O.B is referred to as an "Elite Light Vehicle". The medal is named "Seek and Destroy". On Bungie.net, under the "Enemies" tab they are titled "Elite Ranger," subtitled "BOB," and their description is simply "Wipe them out..."

The name "B.O.B" is a reference to Bungie's Marathon video game series. In the series, all of the encountered human characters, besides the player, are known as "B.O.Bs". "B.O.B" is an acronym for "Born on Board", a reference to the characters having been born on board the titular colony ship. The AI Leela instructed the player to save as many as possible, but Bungie encourages the player on secret terminals to kill them all. The Vidmaster's Challenge states that the player must "Never, ever leave a single B.O.B alive."

BOBs are considered easter eggs, and thus have no canonical explanation in the Halo story.

B.O.B locations
Basic multiplayer map knowledge is helpful to finding some B.O.Bs.

Winter Contingency

 * Three separate B.O.Bs have been discovered on this level, all of which appear near the three civilian settlements in the second portion of the level, and all of which will wield Plasma Repeaters from Easy-Heroic difficulties, and Concussion Rifles on Legendary. It is important to note that their spawning location depends upon how the player approaches the three settlements, and once one spawns, the others will not appear. When using the glitch that causes the player to fly the Falcon that Jun normally rides in it is possible for the level's three B.O.Bs to hijack the Falcon and use its chaingun on the player if the player gets too close to one. Often a checkpoint will occur as it hijacks the Falcon causing the mission to become almost impossible to complete as it will shoot you down constantly. The first B.O.B may appear at the first encountered settlement if the player stops to engage the Covenant forces there. This B.O.B will spawn at the side of the building and will immediately set off along the road to the riverside settlement once spawned.
 * The second B.O.B will spawn at the cliffside settlement if the player bypasses the first settlement altogether. The B.O.B will appear in the upper level of the structure and like the first B.O.B, will plot a course for the third settlement as soon as he spawns.
 * If a B.O.B did not spawn at either of the above locations, then he will spawn within the riverside settlement once the player enters the area. The B.O.B will then dash across the bridge and head up the road to the cliffside settlement.
 * On Legendary, at the very beginning of Winter Contigency, an Elite Covenant in active camoflage will dash to the right and disappear about where the Moa appear. He is often referred to as Bill, so as to distinguish him from B.O.B., with whom he is often confused. If killed, he will drop a data pad (pick it up and read it). He is neither a Ranger nor golden (he's a coppery color, as can be seen in theater mode), and his death does not earn one an "Elite Light Vehicle" kill in the carnage report, nor a Seek and Destroy medal.

ONI: Sword Base

 * In this level, a B.O.B will spawn in one of three locations. Each B.O.B encountered on this level will be a randomly-generated Elite wearing white armor and dual-wielding plasma rifles. The first and second can be found in the Courtyard area. The first is on the right, and the second is over on the left in the area where you started the level. If one spawns, the other will not.
 * The third B.O.B will spawn in the room below the damaged area with the General Elite. He will be under attack by some Marines across the bridge. If you sneak up on him, do not assassinate him as the amount of time you have to kill him will likely run out, and he will disappear in the process. Also, you must attack him first before he attacks you, so make the initial strike count.

Nightfall

 * Another one can be spotted behind the far building at the start of the level. You can find him here.
 * Another one is occasionally spotted on top of one of the buildings in the beginning of the level, where you first go sniping.
 * When you get to the section where you assist the local militia, reminiscent of the Firefight map Waterfront, there will be a B.O.B walking on top of the buildings, this also happens on the "I'll Just Leave This Here" chapter.
 * Yet another one can be spotted among some Jackals around the area where the platform where you battle the Hunters are located, reminiscent of Multiplayer map Powerhouse.

Tip of the Spear

 * As you head for the first AA gun, there will be a hill to the left, a B.O.B will sometimes spawn there.
 * After your Falcon crashes, a B.O.B can be found near the first bravo objective in Invasion on Spire. This B.O.B always wields a Fuel Rod Gun so he is very dangerous, especially on higher difficulties.
 * Another one on this level will occasionally spawn, again with a Fuel Rod Gun, among the Skirmishers and Grunts. Note that if this one spawns, the one above will not.

Long Night of Solace

 * At the beginning of the level after securing the beach, when marines are fighting the covenant forces being dropped from Spirit dropships wait for three deployments to occur. After that, a B.O.B will be deployed in a Drop Pod further along the route you took to get to the facility. Be aware that you can and must see this B.O.B being deployed from a maximum distance of the entrance to the facility. If you do not see the B.O.B emerge from the pod he will instantly vanish.
 * The B.O.B is located in the control room near the end of the level. More specifically, it is working on the terminal near the back of the room. If you are quiet enough, you can assassinate him for an easy 'Seek and Destroy' medal.
 * Another B.O.B also spawns when you have to defend the Pelican, it is on one of the platforms as soon as you enter the room. Try to snipe him, although this method almost always results in failure due to the fact he runs behind a shield, making it very difficult to shoot him. Be aware though, because if this B.O.B spawns, the one mentioned above will not.

Exodus
During the first barrage of suicide Grunts, there is supposedly a Golden ranger Elite that can be briefly fought before disappearance. If it is factual, no one has reported killing him. Banshee B.O.B.s cannot be hijacked. Destroying them does not earn one a "Seek and Destroy" medal, nor an "Elite Light Vehicle" kill.
 * There is a Banshee B.O.B which sometimes spawns shortly after boarding the Falcon on the helipad. Like the New Alexandria Banshee B.O.B, this Banshee will not shoot at you and boosts constantly. In order to have a chance at wiping out this B.O.B, you must board the right (passenger, or starboard) side of the Falcon which lands on the right side of the helipad. This requires killing the Marine which usually occupies this seat if playing solo. The Banshee will come from the same location that the Banshees came from when you first receive the jetpack.
 * There is a Banshee B.O.B that sometimes spawns in the area between check point alpha (where one gets the jetpacks) and the landing pad. It is in the open area that the snipers (with beam rifles) shoot across. The trigger seems to be crossing the lower bridge. B.O.B. appears far right and flies through, then shrinks and often crashes into a building.
 * There is a Banshee B.O.B which sometimes spawns during the missile battery activation sequence in the Beachhead area at the end of the level. The trigger for this B.O.B to appear seems to relate to crossing some point just past the first missile battery (stepping onto the bridge). It spawns somewhat above where the Falcon drops the player off for this area, criss-crosses the area very quickly, and will disappear as it heads in the direction of the previous area's beach. As with other Banshee B.O.Bs, it moves quite quickly and does not fire at the player.

New Alexandria

 * Boosting in the map at a very low altitude on the ground, somewhat near the Club Errera area. It flies around an altitude of 100-150m it spawns on the 6 minute mark and a checkpoint may occur as this happens. It is incapable of fighting against the player and can only boost. It will fly rapidly to Club Errera, it will stay in the area for a few minutes, before flying outside the map's boundary and a checkpoint will occur as it does this.

The Package

 * When the player enters the courtyard, instantly turn left. On the side of the bridge where the Bridge spawn is in firefight, the B.O.B will be there, escorted by three Jackals. This B.O.B will only attack with melee and grenades. It is best to kill the Jackals with a grenade before engaging the B.O.B, and, if skilled, the player can lure it down for Noble Team to take care of.
 * In the section of Sword Base with the Spec Ops Elites, dash past them and the General, and go through the door on the far right. In the room should be a B.O.B with an incredibly fast disappearance time. Be careful with him, as he is very clever.


 * In the battle outside of Halsey's lab, at the end, when a Phantom drops off a second Wraith at the end of the ice shelf, it will also drop off a lone B.O.B.

The Pillar of Autumn

 * When finishing the canyon area of the map (the area with numerous Drones), grab the Laser and look to the opened area in the mid-point of the area which is designated as Boneyard in Matchmaking. This one is clever, so only engage if you are very skilled in lasering enemies.
 * After the mentioned area, go up the stairs and pick up the Sniper Rifle and look to the garage(where the Scorpion and Warthog spawn in the Invasion mode of said Multiplayer map). A B.O.B will be there if the previously mentioned one does not.

Lone Wolf

 * After fighting your enemies from anywhere from 3 1/2 to 11 minutes, a B.O.B will appear wielding an Energy Sword. He is the same color as the General class elites attacking you, so he may go unnoticed. Also, since the B.O.B spawns out near the Wraiths, it is possible for him to be splattered by one of the tanks on his run towards the player, making it seem as if he never spawned. This BOB was likely placed to kill a player who has been playing on the level for too long, as B.O.Bs are more powerful than standard Elites, and this B.O.B is particularly aggressive.

Trivia

 * The BOB's primary weapon seems to be the Concussion Rifle as it is what he is seen using most of the time. But B.O.B's have been sighted using other weapons too.
 * Each BOB has a set time limit before it vanishes. For some B.O.Bs, this time frame begins as soon as it is alerted to the player's presence. For others, the countdown begins once the player enters a certain area, thus it is possible for the player to miss the BOB entirely if it is not spotted. Also, if you assassinate a BOB, it might disappear. If it does, you'll be assassinating air.
 * In Halo: Reach all ranks of Elites, even Elite Ultras, even though they're already white, can be B.O.B's.
 * In the level ONI: Sword Base, B.O.Bs can be any elite armor variant.
 * On 1/19/11 Bungie revealed the location of a Gold Ranger-class Elite in the Challenge titled: "Golden Tree City" the description read: "Find and kill the Gold Ranger-class Elite in a Banshee, fast and low, while on New Alexandria, on Legendary". Whether or not he is a BOB is unknown, as even though all Gold Ranger-class Elites are B.O.B's, killing this specific enemy doesn't result in a Seek and Destroy medal, nor the mention of an "Elite Light Vehicle" in the carnage report, even though it fits with the classical description of a B.O.B, as he is in a very fast Banshee which avoids combat, and whose tail is permanently lit even when the vehicle isn't boosting making it look largely different than other Banshees. As he is in a driver-less Banshee, there's no body seen when the Banshee is destroyed, so it is impossible to check if he is indeed a Gold Ranger-Class Elite. This, along with the fact that he gets killed while inside a vehicle, and not directly by the action of the player, could also explain the lack of an actual B.O.B kill, and its absence from the carnage report as well as the lack of a Seek and Destroy medal.
 * Only one B.O.B. will appear on any mission, though it is possible to kill a B.O.B. and "Revert to last save" before reaching another save point. In this way, multiple "Elite Light Vehicle" kills can be racked up in the same mission
 * The only B.O.B's seen up to date are all Gold and White in armor color and all Sangheili ranks in Halo Reach (Minor-Field Marshal)
 * Most B.O.B's are seen with Dual Plasma Rifles, Fuel Rod Guns, Concussion Rifles, and Energy Swords (Energy Sword Seen on Lone Wolf, only one).