Immobile Banshee

The Immobile Banshee glitch is only available for Halo: Combat Evolved. First, grab a Banshee and place it near a Scorpion. Get out of the Banshee and ride the tank. Using the tank, push the Banshee so that one of it's Gravity Pods is stuck into a crevice on a wall. The tip of the Banshee's wing should get stuck into the cliff wall and the Banshee can't move, even if you try to flip it or throw grenades at it. Be careful though, playing with the immobile Banshee can be dangerous. When you try to flip it while you are near the wall, you might get squished.

It sounds impossible to do, but with a little luck and a lot of patience, it is possible.