I will third, (or is it 4th) Evanovich's Plum series. Imagine slapstick bounty hunting. With hilarious characters.
I've also listened to the first of Jasper Fforde's Thursday next series. It was definitely odd and interesting, but I'm not sure it's laugh-out-loud funny. However, I feel the urge to go and buy the next one.
Pratchett is the king IMHO.
Good Omens is my favorite.
I couldn't get into Christopher Moore, although I tried.