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 guy with an evil laugh. You can use this as a reaction gif whenever you want to express how vindictive you're feeling. This particular one is from The Planet of The Apes (1968).