Clarification Query: Is this topic for all Star Wars media, or simply the movies? If it is, in fact, for all mediums, then perhaps my dialog gives my favorite away?
For the movies, it's probably either Greivous or Boba Fett. Both of them kick major butt!
In print, though, my favorites are Zuckuss and 4-LOM. Their relationship in the Tales of the Bounty Hunters book is just so...wow...