Layer Cake
I actually had to turn on the closed captions for this one. It ranks up there with The Full Monty and Lock, Stock in the English Accents I Can't Understand category.
Once you get past the accents, the fact that I just watched Homegrown last month and this is the same exact movie except Homegrown has Hank Azaria, successfully getting your girlfriend to stop saying "Dumbledore. Dumbledore. Dumbledore. What a fun word to say!" when Michael Gambon walks into a scene, Layer Cake is not half bad. Definitely worth the rental.