Munchkin. It's not just for players any more.
What can a Munchkin RPG GM do? Whatever he wants. Player annoys you? Kill him. Or change his sex. Or turn him into a Canada goose. Go all the way and turn him into a dead sex-changed Canada goose. No one can stop you.
When you're the GM, the rules are only suggestions. So the Munchkin Master's Guide is 48 pages of magic items, NPC classes, and a loaded 100-sided die's worth of dirty tricks . . .
It's GOOD to be the GM.