Damn, that doesn’t work in the subject heading? Sheesh.
The shootout that ends the intro sequence in Leone’s Once Upon A Time In The West has always been my favorite.
Pacino screaming (with an unloaded gun) "You think you’re big time??? You gonna DIE BIG TIME!!! in Carlito’s Way
Cagney in White Heat
The “forced” showdown in between Henry Fonda and Lee Marvin (with John Wayne as the sniper) in The Man Who Shot Liberty Valence
El Mariachi, baby.
Not a shootout but an epic showdown…
The Last Seduction…if you haven’t seen it go rent it asap…classic movie that should have been nominated for Oscars but the production company fucked up and showed it on HBO before releasing it 
Ant situation where Bridget/Wendy feels trapped…especially in the last scenes are jawdropping. What she does to get her way…I don’t want to spoil it for those who haven’t seen it.
For those who have…didn’t the last scene in the apartment make you gasp or think she did not just do that?
The French Connection where Gene Hackmans character loses it at the end. Not a fantastic blood 'n guts type thing, more of a “hey, what’s just happened?”
Wasn’t it James Stewart and not Henry Fonda? Still a good showdown, though.
What about “The Shootist”----I thought that was a good one.
More votes for Desperado, Heat, The Killer, The Profesional, Reservoir Dogs The Matrix, Unforgiven and Last Man Standing.
Further votes for:
The Terminator (“I’ll be back”)
T2 (“He’s not dead.”)
Best cheese shootouts:
Grosse Pointe Blanke
Hotshots!
Hard Target
The Art Of War (The shootout in the hallway, where both gunners empty out their clips at each other Matrix style, and miss with every single shot)
Riding Bean (Very cool anime shootout/carchase involving, among other things, hand grenades)
Gonna have to say here that I thought the Way Of The Gun was terrible. The acting was lousy, the gun fights were sparse and flat, and the plot was convoluted.
My ghod, am I the only one who remembers a little Clint Eastwood gem called “The Gauntlet”??
They had to stop making shoot-em-ups for three years to get the supply of blanks back up to normal. 
The final showdown in Mexico in Extreme Prejudice.
Definitely Leon vs NYPD in The Professional.
Also, Buddy vs the nomadic cave people types in Six-String Samurai.
Yes, it WAS Jimmie Stewart… i don’t know what the hell i was thinking about. Maybe Firecreek. Me am dum.
John Wayne vs. Robert Duvall and company at the end of TRUE GRIT.
Duvall calls Rooster Cogburn/Wayne a “one eyed fat man”, and Wayne bellows back “Fill you hands, you sone of a bitch” and charges across the valley floor with guns a blazing.
Now that’s a great shoot-out.
Let’s not forget all the great shoot-out scenes, especially the one in the beginning, in The Replacement Killers. Chow Yun Fat is the man. The cinematography in this scene kicked ass, in how it kept switching between slo-mo and regular motion. Also, the way Chow continually disappeared at key points and reappeared somewhere else was great. And let’s not forget that this was all done to “Busy Child” by Crystal Method. Without a doubt, this one one of the best shootout/massacres of all time.
I have to agree with the beginning of Desperado. If it wasn’t for the “…and in walks the BIGGEST MEXICAN I’ve ever seen…” scene, that movie wouldn’t have been as cool as it was. If you liked Desperado, you’ll like El Mariachi, too.
How about Tombstone? This flick has showdowns and shootouts. Take for example when Wyatt disarms Curly Bill and his gang comes out to get him set free. Wyatt is all alone except for a drunken Doc Holliday, who is told he’s so drunk he’s seeing double, to which he replies “I’ve got two guns: one for each of you.”
It gets even better when he puts this huge .44 peace-maker to Ike’s head and says
“You die first, get it? Your boys might take me in rush, but not before I make your head into a canoe.” One of the gang says he’s bluffing, but Ike looks into Wyatt’s eyes and knows better. They back down and leave, and Curly Bill spends the night in jail. Awesome.
Even before this all goes down, when Wyatt throws the bullying dealer out of the Oriental is terrific. He’s not even armed. Talk about some major league shit talking:
<Wyatt slaps bully dealer>
“Throw down, boy.”
“Now mister I’ve had just about-”
<slaps him again>
“I said skin that smoke wagon and go to work.”
“I’m agonna-”
<Slaps him yet again>
"You gonna do something, or just stand there and bleed? That’s what I thought. <takes gun> Now get out of here and don’t come back."
That’s kinda sorta how I remeber it, so it’s not too accurate, but it’s the jist. Besides, the “stand there and bleed” part is the best anyway.
How about in Con-Air when Nick Cage takes out 3-4 bad guys in like 5 seconds. That rocked. The showdown that followed between Nick and John Cusack was pretty cool two: “There’s only two men I trust in this world. One of 'em’s me, the other’s not you.”
the shootout during the bank robbery in Heat sticks out in my mind as exceptional. It’s very loud. You know, the one with Robert DeNiro, Val Kilmer, and Al Pacino.
A classic is the machine-gunner’s eye view during All Quiet on The Western Front. Saving Private Ryan had some of that as well.
Excruciating was the sniper scene in Full Metal Jacket.
Speaking of sniper movies, go see ‘Enemy at the Gates’. Not only does it have some of the most harrowing large scale battle scenes since ‘Saving Private Ryan’, it’s got some pretty cool sniper duels.
It’s got some romance too, so you can bring a lady friend. Provided she can handle the blood and brains exploding.
Nobody’s mentioned Waterhole #3. James Coburn and Carol O’conner going at it with shotguns and not wanting to get shot.
forget the Woo films and influenced one. its eye candy movign too fast to focus on a single element.
I love, love, love you for mentioning that one! I respectfully submit this as one of my all-time favorite bad movies.
Oh, and whoever mentioned Replacement Killers, that one rocks, too.