Colossus vacation
From Halopedia, the Halo wiki
On the level Colossus, go to the bottom of the level where the windows are ( orange sky) these are the windows flanking the overshield, not the ones directly next to them. Crouch and go as far into the corner as you can. Keep crouching, and press A many times, then walk onto the glass part, you should fall through the glass out of the level. You can't really go anywhere, but you can cut yourself in half. Simply face towards the glass and walk backwards. Master Chiefs guts certainly look strange.