Bug: Multiplayer Burial Mounds: If you smash another player against a certain pillar with a vehicle, they will fall through the map. If they are lined up right, they fall onto an orb out of map that is actually the sky box housing for the textures around the map. They will partly fall into it and their image will then suddenly be plastered all over the sky as a gigantic Master Chief corps.
Bug: On the multiplayer level of Zanzibar, this is done with a Specter. The the right side of the generator building, there is some rubble and a door with 3 Plasma grenades next to it. The natural wall next to the building is at an almost 90 degree angle. If you hit this wall just right with the Specter, it will suddenly begin climbing the wall almost straight up and it will take you to the roof of the generator building.