Invisible bridge glitch

The Invisible Bridge Glitch can only be found on the Halo 2 levels, Delta Halo and Regret.

Delta Halo
Once you begin the level, jump on the hill with the Grunt on the Plasma Cannon. Jump up until you are on top of the map, and then go to the bridge area (if there are enemies around and Prophet of Regret hologram is on the hologram, you messed up). Walk on the area the bridge would be. Walk into the void where the bridge would be, and you will find that you aren't falling.

Regret
There is also an invisible bridge glitch on the level, Regret. First, progress as normal to the building where you fight Regret. Before the cutscene commences, get the gondola near the platform of the building. Once there, hurry and jump over the area the bridge is supposed to set up. If done right, you will activate the cutscene with the SPARTAN-117 walking on thin air. You will also be able to see the Marines, if they were at the boarding platform.