[Mauser]

Here are some I like in no particular order.

The Shootist - John Wayne’s last shootout.
Scarface - I Love Pacino's energy during the scene.
The Way of the Gun - I thought the shootouts were pretty cool.
They Live -"I have come here to chew bubblegum and kick ass, and I’m all out of bubblegum", enough said!
The Wild Bunch - Probably the coolest cast of characters firing a countless number of rounds.
The Devils Rejects - The opening shootout (The only good part of the movie IMO)
The BooneDock Saints - I love when they shoot it out with Il Duce and Dafoe's line "And there was a firefight!”
Platoon - The final battle.

I’m surprised no one mentioned The Wild Bunch or Scarface.