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 possible for B.O.B.s to use Armor Lock.

Description
You do recieve 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". On Bungie.net, 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 onboard 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. It has been theorized, however, that they are Ossoona, hand-picked spies for the Prophets.

BOB 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. 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.

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 combating some Marines across the way. If you sneak up on him, do not assassinate him as he will disappear in the process. Also, you must attack him first before he attacks you, so make the initial strike count.

Nightfall

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

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 when securing the beach, wait for three deployments to occur. After that, A B.O.B will be deployed in a Drop Pod.
 * 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.
 * Another B.O.B also spawns when you have to defend the Pelican, it is on one of the platforms. If this one 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 been reported of killing him.
 * 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 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. 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.

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 BOB will be there, escorted by 3 jackals. This BOB 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 incrediby 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 aforementioned 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 BOB 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 BOB 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 BOB 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 BOBs are more powerful than standard Elites, and this BOB is particularly aggressive.

Trivia

 * The BOB's primary weapon seems to be the Conncussion Rifle as it is what he is seen using most of the time. But BOB's have been sighted using other weapons too.
 * Each BOB has a set time limit before it vanishes. For some BOBs, 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 BOB's.
 * In the level ONI: Sword Base, BOBs 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 BOB'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 BOB, 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 driverless 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 BOB kill, and its absence from the carnage report aswell as the lack of a Seek and Destroy medal. Still, this is the only Gold Ranger-class Elite known to be in New Alexandria, the only mission left where none were ever killed is Exodus, as there has been an unconfirmed sighting early in the level.