Those that make you go...
Anyway, I am particularely thinking how much I love to laugh at books, and books that are so ridiculous I can't control myself from laughing a full belly laugh out loud, maybe in public, maybe in class, maybe on the bus. Of course it gives new meaning to "laugh out loud" when the crazy person on the bus starts laughing for no reason while reading, but oh well. I figure I am having a better day than anyone else if I can have a good laugh for "no reason".
Douglas Adams, Hitchhiker's Guide to the Galaxy Series
Sherman Alexie, The Absolutely True Diary of a Part-Time Indian
Lousie Rennison, Angus, Thongs, and Full-Frontal Snogging
William Goldman, The Princess Bride
What makes you laugh? Laugh until it hurts? Laugh until you cry? Laugh until your partner wants to lock you up? Makes you laugh in public and get weird looks?
At least this last gif should give you a giggle.