Here we go I'm going to shatter this list with some overpoweringly awesome if obscure 70s films.
Bring Me the Head of Alfredo Garcia. The ultimate Peckinpah film and the most twisted display of violence and nihilism in 70s film. Warren Oates, possibly the coolest son of a gun ever to act in a film, kills a lot of people with a Colt Commander.
Get Carter. Michael Caine being almost as awesome as Warren Oates, rampaging like King Kong through the filthy Brutalist styled streets of England. Possibly the best British film of all time. He packs a Sig P210 and a double barrel at different points of the film.
Point Blank. Lee Marvin packing a .44 Magnum four years before Dirty Harry. He doesn't actually shoot anyone except a bed (possibly because he's a ghost), so perhaps this is dubious, but Lee Marvin is so cool in this movie that butter wouldn't melt in his mouth. He's even cooler in the '64 remake of The Killers. So cool he blows away Ronald Reagan, who seems to be playing himself, like it's an afterthought.
Prime Cut. Lee Marvin and Gene Hackman. Rednecks. Men being turned into sausages. Naked women. Lee Marvin buzz-sawing through a field of sunflowers with a Smith & Wesson Model 76 and driving through the heartland in the biggest, blackest Cadillac you ever saw blasting some kind of Irish punk rock. It is impossible to watch this film without wearing a cockeyed grin the whole time.
Rolling Thunder. The most insane and over the top violent 70s film of all. It has literally everything you can hope for from a 70s movie. Vietnam veterans suffering flashbacks. Bloody revenge. A giant Cadillac. Nudity. A gunfight in a Mexican whorehouse. All dealt by a man with a sharpened hook for a hand.
