I rather like that list. The Wild Bunch has not one but two incredibly gunfights, and that movie totally changed the way gun violence was shown in the movies. And the end of the movie is cool as fuck to boot.
Heat definitely has a great shootout, random, loud and violent. It's cool how they build up the robbers to make them somewhat likable for their professionalism and savvy but then BAM show you how they'd drop you in a heartbeat to get away.
Open Range is easily one of the best shootouts in a western, but it builds on and perfects what many westerns had already done and doesn't really bring anything new to the genre except to do it all extremely well.
I love Woo almost as much as the next action movie dork, but really I wouldn't rank any of his movies in the top 5. Come on, the hospital scene in Hard Boiled is Exhibit A in proving that too much of a good thing starts to bore the hell out of you. I just find Woo's gunfights become dull because the extreme unreality (and yes I know it's deliberate) starts to detract from the coolness. After you see 400 faceless thugs run out just to get shot down (complete with the classic Hong Kong movie extra "OWW, I DIE!!" quality grimace-and-slow-slump to the ground), I start waiting for them to hurry the hell up and get on with the important stuff, like shooting the hero with the prerequesite 50+ bullets it takes to make him fall down the first time. I'm not as much of a fan of Woo's cartoonish and deliberately overdone gun fight style as some, but I agree it's seminal and very popular so you pretty much need Woo/Fat on there.
The apartment gunbattle in "Time and Tide" blows all Woo's fight scenes away IMO.
Oh, and I agree with most of you that Copland is out of place, and I haven't seen State of Grace either. Hmmm.
PEACE.