Gif Central boasts hundreds of funny animated gifs and reaction 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 Michelle Obama giving a thumbs up (note the classic "NOT BAD" facial expression). This can be used as a reaction whenever somebody says or does something online that you agree with.