Munchkin

Q. What happens if the Foof Gun gets hit by Antimatter? Does it always provide a -6 penalty or is its use still optional?
A. Antimatter only reverses the bonus and makes it impossible to get rid of the item without a significant cost, but affects nothing else about it. So, an Antimattered Foof Gun is still optional to use. If you chose to use it, the penalty is -6. If you kill the monster anyway, the monster is obliterated, you gain no Level for killing it, but you do get its Treasure. Consequently, if you do not chose to use an Antimattered Foof Gun, there is no penalty.