Gif Central boasts hundreds of funny animated gifs. Only the best of the best make it onto this site, with most of them having an accompanying source. No tumblr-esque one-second-long disappointments. No obscure titles or descriptions.
This is an animated gif of a character from Garry's Mod turning around before the text "WAT" appears. Garry's Mod is a sandbox physics game that uses the Source engine. I think that the sudden nature of this gif makes it hilarious.