There are a lot of funny games on this page, but what it really comes down to is your sense of humor. If you enjoy sarcastic and silly kind of humor, then There Is No Game is a fantastic one to play. The narrator is kind of ridiculous the whole time, and he is constantly trying to mislead the player in relatively obvious ways. His deep and grumbly voice also adds to the humor.
For those that like inside jokes and quirky dialogue, then Coolmath Games: The Game is certainly for you. It makes a lot of references to other games on the site, as well as a lot of quick one-liners that will have you laughing. It is definitely different than any other game we have, so go and try it out for yourself to see if you enjoy it.