Chuck Palahniuk, author of Fight Club is my favorite. It really sucks that he's become so popular with these wanna-be faux-fringe pricks who dont get understand that his books are attacking their kind of people in the first place. lol.
I also love Poe and Mark Twain.
Here are the 3 funniest books you will ever read:
Confederacy of Dunces
Thank You for Smoking.