In Gears of War 3 for the Xbox 360, you can unlock the Laugh Track mutator, which will replace the standard kill commentary with some mature humor, and has no other negative or positive effects.
To unlock the Laugh Track mutator, you need to complete the regular campaign, Arcade campaign, Beast mode, and Horde mode on at least casual difficulty.
Check out my other guide if you’re looking for the full list of unlockable mutators in Gears of War 3.