Type-1 Antipersonnel grenade

"Betcha can't stick it."

- Cortana in the Halo 2 E3 Demo

"Holy light!"

- Grunt combat dialog

The Covenant Type-1 Antipersonnel Grenade, also known as the Plasma Grenade or the Sticky Grenade, is similar to the UNSC Fragmentation Grenade in that it is a thrown Anti-Infantry and Anti-Vehicle weapon.

Overview
The Plasma Grenade is a specially designed explosive device (grenade) that sticks to its targets. Once it has made contact with a target, the plasma grenade will immediately bond to it, making any efforts of removal futile. The bonding mechanism holds its attraction until detonation, making it impossible to avoid its deadly explosion. Although it will bond to any target it hits, if it attaches to a piece of armor or a weapon, removing said articles will allow one to distance themselves from the explosion.

The "sticking" mechanism is complex enough to allow the plasma grenade the ability to distinguish between targets and inanimate objects. For example, it will stick to a soldier or a vehicle, but not a tree or a wall. This does not, however, allow the grenade to act selectively. The plasma grenade will not distinguish between friend or foe so accuracy and caution ARE strongly advised when throwing it.

The plasma grenade possesses a timer. It has a three-second fuse that counts down at the point of activation. A manual activation via a small button or a stimulated activation, such as another explosion or gunfire, will set the detonator and start the countdown. Delayed activation can also set the detonator after it either sticks to a target or otherwise comes to a rest. It is possible to tell if the grenade has been activated. A densely small and bright cloud of plasma emission will leak around the grenade as the explosive reaction takes place inside. This cloud will gradually grow to a larger diameter after each second of the countdown. A low sound is emitted by the grenade when activated, followed by two rapid beeps and a high-pitched whine just nanoseconds before the explosion. This is the plasma grenade's standard process of detonation.

The Plasma Grenade appears to have two settings: the standard three-second fuse and a delayed manual detonation. The latter is seen in Halo 3 by suicidal Grunts hoping to ensure their enemy's death by exploding right next to them. In addition, the plasma grenade like all grenades can be destroyed by being shot(Easily seen with the Sentinel Beam).

Also some characters in campaign cannot be stuck. brute chieftains have immunity from this until there armor is knocked off. Also on lower co-op difficulties in Halo 3, allies cannot be stuck.

Advantages
Sticking an enemy with the plasma grenade will always kill them when it detonates, no matter what. Even a fully shielded Spartan or Elite (with the exception of higher-ranking Elites like Ultras on higher difficulty levels) cannot withstand a stuck plasma grenade. The plasma grenade is slightly more powerful than the UNSC fragmentation grenade. If it goes off at the base of the target's feet without bonding it still results in a kill.

Disadvantages
The plasma grenade's bright blue glow and longer delay fuse allows enemies to easily notice and avoid it. It can not be used around corners well, as it does not bounce, nor does it roll. A player wearing a fully charged Overshield may be capable of surviving the blast even when stuck. Also, if a smart enemy is stuck when they are too close they can simply run toward you to catch you in the blast zone. In Halo 2 and Halo 3, a primed plasma grenade in flight can be detonated mid-air by another explosion. Weapons capable of this include the Rocket Launcher, Brute Shot, Missile Pod, Frag Grenades, other Plasma Grenades. The Plasma Grenade will not stick to certain types of armor such as that of a scarab or a Brute Chieftain's. When thrown at them, the grenade will fall to their feet, and they will probably notice it and move out of the blast radius. Ballistic or explosive weapons such as a shotgun or brute shot will remove the plating allowing the grenade to stick.

Effects on Health
It has been shown that prolonged exposure to the radiation emitted by plasma grenades, without proper protection, can cause a deviation in the neural electric pathways of the user--a disorder called Boren's Syndrome. This disease can be fatal if the person does not get treatment. Avery Johnson is the only known person to have Boren's Syndrome.

Theory about "Stickiness"
Note: The following is speculation and is not considered fan fiction.

The plasma grenade may stick by producing a thin layer of plasma which, when in contact with a target, fuses to the target. The reason the plasma grenade sticks to vehicles and characters may be due to an ability to sense heat. Body heat and the heat from vehicles engines is most likely what causes it to stick. Since a "dead" wall doesn't emit heat, it will however stick to the "living" walls of a Flood Hive.

It is also theorized that there is a complex internal mechanism built into the grenade that gives it this characteristic. A gravity generator may be built into the core of the device, giving it its own force of attraction. This artificial force of attraction is highly concentrated, which is exactly why the grenade is impossible to remove.

Another problem to the stickiness, is the reason when a plasma grenade is primed, it does not stick to the thrower afterwards. A theory for this could be that the grenade must be primed touching something emitting heat, then leaving the heat-emitting object, thus becoming "sticky," and finally landing and sticking to another object emitting heat. Or it is possible that it is equipped with a timer, so the thrower isn't stuck.

Another reason is the plasma heats up and is super heated and then by the time it touches it, it melts the armor or whatever and sticks to it.

It is possible that the grenade has an adhesive activated by a timer. Once the grenade is activated, this timer is initiated, giving a few seconds for the thrower to release the grenade. Once the timer has run out, the adhesive activates and the surface of the grenade is a sticky as glue.

Trivia

 * In Multiplayer, if you stick an enemy with the plasma grenade you are awarded with the Grenade Stick Medal.
 * In Multiplayer there is sometimes an error where the stuck grenade will only kill the opponent. There are also occasions where a Plasma Grenade will pass through the opponent or if it does stick, it may not kill them for an unknown reason.
 * In Halo: CE the Plasma Grenade's explosion was more of a blue cloud, similar to that of a needler in Halo: CE. The size of the blast animation also got smaller going into Halo 2, and smaller still in Halo 3,
 * In Halo 2, when the Covenant use plasma grenades in battle, they will shout phrases as they throw them, such as "cleansing flame", "flare" and "holy light". This is similar to their belief of Halo.
 * If John-117 throws a plasma grenade, the Covenant will call it a "demon flare". However, when the Arbiter throws a plasma grenade, Elites and Grunts will still address it as a demon flare, even if the grenade is a frag. This may prove that all kinds of enemy grenades are demon flares. This may be as a kind of slang, with "demon" referring to the enemy, or enemy thrown grenades, and only in the opposite manner.
 * Often times, when an NPC is stuck, they will have some type of reaction to being stuck.
 * Occasionally, if two plasma grenades are thrown in succession at the same spot; one will detonate, launching the other into the air. The airborne grenade will explode in mid-air, causing a "fireworks" effect. This was easier to perform in Halo: Combat Evolved.
 * If you stick a charging Hunter with a plasma grenade the Hunter will instantly turn around, exposing its back, when the grenade explodes.
 * In Halo:CE or Halo 3, if you throw a Frag grenade where a group of plasma grenades are, the detonation of the frag will make the plasma grenades explode.
 * In Halo:CE, Plasma Grenades take 4 seconds to detonate. In Halo 2, they take 3 seconds. In Halo 3, they take about 2 and 1/2 seconds.
 * On one side of the Plasma Grenade, a Forerunner Symbol like that of Halo:CE Elite is visible.
 * In Halo 3, when you throw a plasma grenade, it makes a long beep before exploding.
 * Blue-Balled /blü bŏld / adj: describes when a person has been stuck by a plasma grenade, and a plasma grenade only, in the crotch. The blue is named for the blue explosion of a plasma grenade, and the balled is for the grenade stuck to the crotch.
 * Plasma Grenades are favorite weapons of the Player Ghosts of multiplayer maps, nearly always sticking people in the face and chest.
 * In Halo 3, physics made it possible that if timed correctly at a position, when an opponent's Plasma Grenade is aimed at a player's left elbow (virtually), and when the grenade itself is about a foot away and the player throws his/her own Plasma Grenade, the both plasma grenades will stick each other and explode midway in the air.
 * It is possible to stick the grenade while it is in the opponent's hand, meaning they get to throw two grenades at you.
 * It has been found to be possible to stick yourself.1