A Clarification and Mini Discussion:
Naturally, all three of these feature Tommy Guns.
The St. Valentine's Day Massacre is a 1967 film based on the infamous incident, as noted in the Chronology.
Little Caesar is a 1931 movie about the rise of a mobster named Caesar through his mob and eventually gets into the upper heights.
The most interesting one, though, is The Public enemy, another 1931 film. It's about two young boys, Tom Powers and Matt Doyle, who grow up together in the 1920's. Tom ends up succumbing to corruption and joins the mob (and is often referred to as Tommy, eh heh heh). He has an older brother who served in World War I, and they are at odds because they are on different sides of the law. One particular sequence stands out:
Tom Powers: So beer ain't good enough for you, huh? Mike Powers: Do you think I care if there was just beer in that keg? I know what's in it. I know what you've been doing all this time, how you got those clothes and those new cars. You've been telling Ma that you've gone into politics, that you're on the city payroll. Pat Burke told me everything. You murderers! There's not only beer in that jug. There's beer and blood - blood of men! (Mike throws the keg into the corner, smashing Mrs Powers' table and causing a racket) Tom Powers: (Stands) You ain't changed a bit. (Tom walks away, but turns for the last word]) Tom Powers: Besides, your hands ain't so clean. You killed and liked it. You didn't get them medals for holding hands with them Germans.
Although not directly related to the Tommy Gun, the sequence certainly seems to have some interesting parallels--for one, Tom being named Tommy obviously is meant to reference the Tommy Gun, showing just how iconic the gun is when paired with a gangster. There's also the conflict of how the same gun was used in military and in gang wars--in a lot of ways the scene almost plays out like a vision in John Thompson's head as he struggles with how his creation turned out. And we also have to wonder--why, exactly, is there always violence, even when its only a discussion? Excitement, sure, but especially in these early gangster movies conflict seems to be inseparable from violence.
(Quote used from http://www.imdb.com/title/tt0022286/quotes)
