Righteous Kill is a pretty good NY city cop thriller with a few twists you won't see coming. I'm a little surprised they cast De Niro and Pacino in it, unless those two were just looking for a movie to do together or something. They're good, don't get me wrong, but overall the movie just isn't the quality that you'd expect from something with both of these guys. It's probably not fair, but you sort of expect amazing, not just pretty good.
At any rate, definitely a worthy rental if you like fairly dark cop thriller type movies.