The Fate system from Evil Hat is possibly one of my favorite modern RPG systems. For me, it hits the sweet spot of mechanical complexity, where players have interesting tactical choices to make in a conflict, but aren't bogged down by needless complexity. Each iteration the game goes through refines it even more, from its beginnings as a set of diced rules for Amber to the latest expression, the Dresden Files RPG.
I am also partial to a good caper: heists, grifts, and cons make for great viewing. Until the Leverage RPG comes out, though, there's not much in the way of support in the RPG world for that type of game - but Fate's aspects seem perfect for the kinds of problems that grifters and thieves run into, and giving the players power to make declarations can produce a more involved caper than if the GM has to make everything up on his own.
