The Covenant plasma grenade is one of the more clever weapons in the game. The plasma grenade has the ability to distinguish between organisms and scenery. A plasma grenade will stick to organisms and explode three seconds after contact with that organism. It is also able to stick onto vehicles. The plasma grenade will also explode three seconds after coming to rest.
In Halo 2, the Plasma Grenade will kill anything that it is stuck to, with the exceptions of Hunters, vehicles (excluding Ghosts and Banshees), Brute Captains (Legendary only) and SpecOps Elites (Legendary only). Its splash damage and shield-draining capacity have been significantly reduced from the original. However, the weapon does seem to have a "bewildering" effect on hunters, who will wander aimlessly after a direct plasma grenade hit. This enables the player to easily achieve the orange-spot shots needed to dispatch the hunter.
In multiplayer, it is possible to survive being stuck if you have a full overshield and if the "damage resistance" option is turned on. After the auto-update, you can even die in one hit if it explodes at your feet, regardless of whether it stuck you or not (assuming you don't have an overshield).