Ok, so this glitch is in Halo Reach, what you do is start up a forge game on any map, place an Armor lock ability, then once you pick it up and use it. As a Spartan/Elite quickly change into oracle/forge mode while STILL HOLDING DOWN the button to use armor lock, and delete all the armor locks on the map using the Delete All feature, this will delete the ability that you are using too. This is GOOD, once they are all deleted switch back to your person mode and Presto! You should now still be using armor lock although you do not have it. You can still move around, fire guns and intercact with everthing, the only difference is that the only way to die is by natural causes. (i.e. Falling of a cliff, kill boundries, and assassinations)
In addittion to this you can still pick armor abilities as normal, however, once you die or use armor lock again, it will no longer work. You will have to do it again. Note that this only works in forge. Forge and ONLY Forge mode. This is to prevent cheating in online games.
Well, that is pretty much all there is to it. The rest is up to you to discover.
Have fun glitching!