There are glitches that just ruin the balance of the game, and its no longer fun.
I have no idea what the MW 2 glitch is per say so can the players actually explain it.
Basically you turn yourself into a walking bomb that has a really big explosion as soon as you die. So you run into a group of enemies and let them shoot you and you kill them. If they dont shoot you, you can just knife them or something. Pretty much a lose lose situation for anyone whos is not doing it.