Therminator
Rock Star
Silver Level
I use DriveHud because it's the only one that works with BetOnline which I must play on because it's the only site that'll work in New York State (as far as I know) where online poker for real money is illegal. I assume it works pretty much the same as the other HUDs. Sometimes the numbers seem hokey, especially for tournaments, but bottom line, I use it all the time.
Poker tracker 4 or hold'em manager. Both have 30 day free trials I believe and both can be purchased for $100 for NL holdem with out Omaha. If you play Omaha too I think it is $150.