This has nothing to do with the characters, just the names. Which ones rub you the wrong way, and why?
For me, the winner is Count Dooku. Like I've said before, it sounds like the sewage auditing job no one wants. "Excuse me, Anakin, but this burrito isn't settling with my stomach. I have to go and count dooku."
For the EU, Vandolay. There's a place for decent homage, and there could've been a clever way to reference Seinfeld (A'bubot could've been a less obvious one that fans would get). But to tack George's alias on a Imperial grunt who looks nothing like Jason Alexander and for no reason, that is the definition of fail.
EU runner-up would be Soon Baytes. Honestly, man, that's just bad. I hope someone at Lucasfilm got fired over green-lighting that one.
Film runner-up, definitely Commander Cody. Cute. An homage to both a one-hit wonder and a forgotten serial. Ha ha. Beat us over the head with it, why don't you? Why weren't the other clone commanders called Commander Jan, Commander Dean, and Commander Carl Wilson and have them cruise around in an Intech Sloop John B-409?
I think Jango Fett has a pretty lousy name, too. That worked once, for junior. Not so much for daddy. It just lacks the ring of the original. "This is Boba Fett, the notorious bounty hunter. His father was Jango Fett. No, the bounty hunter Jango Fett, not the French jazz guitarist Django Fett."