Elevator Glitch

From Halopedia, the Halo Wiki

The Elevator Glitch is a Halo 3 and Halo 3: ODST glitch that allows players, with a partner, get to very high places. This can be done in Matchmaking, Custom Games, Forge, and Campaign, as long as you have a right angle.

[edit] Walkthrough

1. Find a partner and a 90 degree corner that can go higher than around six normal jumps.
2. One person should go and look directly into the corner, than walk straight into it.
3. The partner should stand on the first person's head and do the same.
4. The person on the bottom should start pressing A in a rapid, repetitive way, making sure that both people are looking into the corner and walking into it the entire time.
5. If done right, you will go up until you reach the top, and your partner will be in the, supposedly, "unreachable" spot.