A poster named accident at the Hardfought forum (registration required) has claimed to have used a working Halo aimbot. The article contains no proof-- no movies, screenshots, or URLs-- and don't ask us where to get it, because even if we knew (which we don't) we wouldn't say.

The post also claims various other cheats exist, including a banshee pilot program. We're a bit skeptical of that one.

UPDATE: Claude Errera points out that a film of the Banshee Pilot program (but not the aimbot, at least not so far) has been made.