When the SWAT Team lands in helicopters, the footage is obviously the same landing and SWAT guys jumping out, filmed from two different angles as the three men disembark the helicopter in the exact same order and way both times.
Obvious stuntman standing in for David Bradley, jumping across the cars when the grenades explode, at the end of the opening scene.
In the opening garage shootout, three or four grenades roll under a row of lined up old cars, which Nick then runs across to avoid the resulting explosions, but the grenades only roll a few feet out-under one or two cars at most-while Nick then goes through an elaborate action sequence, hopping from car to car, over seven or eight cars, several dozen feet out, which each car being flipped into the air by grenade explosions.