This is one weird glitch in Lockout.  I found a movie on the internet showing this, and it seemed really weird, so this is why I'm writing this.  In Lockout, you do a sequence of events, and you die instantly in the end.  Here is how to do it.

1. Switch the gametype so that there are no shields.
   
2. Get a Battle Rifle and some other weapon.
3. Start to run.
4. While running, shoot one burst from the Battle Rifle, and press R right after you shoot.
5. Switch to the secondary weapon very quickly.

It is a really funny movie because you see people running, then flip over and die...  Just look at the video.  This glitch might only work on un-updated X-boxes...