call me old skool, but i still love the chariot race in Ben-Hur (1959). my favorite part of it is when the crowd of 8000 random extras thought they were witnessing a real, legit race and got so caught up in the emotion of it that they stormed the racetrack, there are random extras running around and my favorite shot is when the camera shows one guy as he picks up Marsala's helmet, looks around real quick to make sure nobody's watching, and then totally runs off stealing it.

Other than that, the car chase in The Matrix: Reloaded is pretty badass.
The elevator shaft scene in the new Die Hard with the SUV is pretty whack.