The flashbangs in the arena in The Town. 2:06
I just watched Heat on Blu-ray oddly enough and have to say bass is actually kind of disappointing on it, even the airplane scene. On the DVD I recall there being more impact to the shootout scene and better bass in general, but that was also in the days of DVD
I bought Heat on Blu-ray mainly for the shootout scene and the separation is still amazing, but most of the weapons lack "weight". Still one of my favorite movies.
Some awesome newer shootouts that rock audiowise would be The Town (finale), Inception (chapter 6 I think) and Max Payne (chapter 17), awesome bass.
The Incredibles on Blu-ray. Bass is pretty freaking awesome.