DiCaprio, but only for The Departed. He was excellent in that but I've not really liked him in anything else.
Odd one this: Michael Caine. I thought he was a bit of a one trick pony but after seeing more of his films I've realised he is a genuinely great actor.
Pierce Brosnan. I thought he was a bit of a Milk Tray man Bond, but since seeing him in The Matador and Seraphim Falls I've realised he's also pretty good.
Heath Ledger. Thought he was a typical Hollywood pretty boy, then I watched Brokeback Mountain. And he looks terrifying as the Joker - really looking forward to seeing that.