1) My wife.
2) Black hole of amusement. (For instance, building a home-made catapult and having fun hurling dog droppings into the yard across the street. This person would instantly make that unfunny and make you stop.)
3) A person so anti-funny that if you mixed humor and this person together, the resulting explosion would rip away Earth's atmosphere and make it an unliveable planet for thousands of years.
"Shit, here she comes. Damn fun assasin. Hide the catapult."