Robert Rodriguez--he writes practically everything he does, and also shoots, edits, produces, and composes the music for most of it. Plus he has a good sense of humor and knows how to get shit done.
David Fincher--I like dark movies, though Zodiac and Benjamin's Butt were rather long. But Seven, Fight Club, and Zodiac I really liked.
Edgar Wright--I think he's only done two movies (Hot Fuzz and Shaun of the Dead), but I love the emphasis he puts on humorous quick camera shots and double callbacks.
Ridley Scott--nuff said.
Tony Scott--Ridley's bro! Loved Crimson Tide, Man On Fire, Spy Game, and Enemy Of The State.
Guy Ritchie--When he's on form, he does great. Revolver was iffy, and Swept Away was just embarrassing, but his other three are amazing, and Sherlock Holmes looks promising.
Clint Eastwood--Yes he directs, too. Unforgiven is a modern classic, and Gran Torino is hard-hitting and humorous at the same time.
Michael Mann--nuff said.
Christopher Nolan--No, not just because of the Batman movies. Insomnia was some of the best work I've seen Al Pacino and Robin Williams pull off, and Memento was pretty decent, though gimmicky.
Finally, just because I don't think anybody's mentioned him...Ben Affleck. Yeah, he's only done one movie so far, but it's really really good.