Definitely Othello. Best villain ever in that one. Probably Macbeth above Hamlet. Macbeth is like Shakespeare's Hollywood action flick, but there's a lot of depth and political statements through it too. Hamlet is a bit moody, but I've not read/seen it since I was a kid. Unless you count the Disney version. That's about the only way you can improve Shakespeare; add cats.
Incidentally, I called all my Redguard characters in the TES games Othello, and in NWN my Druid had a pet called Iago.
*holy crap* I so need to get in on TES online early, so I can reserve the name Othello.