This is the type of website that makes me upset that I didn't think of it myself: Cumming or Drumming?
The premise is simple. The site shows you a zoomed in photo of just a face, and you have to decide if it's a porn actor or actress orgasming (c*mming) or a drummer making a drum face (drumming).
Needless to say the game is rather NSFW so be careful if you're slacking off at work. Otherwise, play the game and then come back here and let us know how you did.
I got 9 out of 10 myself.