Anti-Hero: Tom is an Unscrupulous Hero for he is a criminal and a deadbeat gambler who sleeps with his boss's girlfriend and backstabs his way through the film. However, he really does care for both Leo and Verna. All his plotting is for their benefit.
Tic-Tac. Moments after Tom has hit a Giant Mook across the face with a chair, Tic Tac strides into the room and without pausing snatches the chair from Tom's hands, whereupon he and the Giant Mook inflict a No-Holds-Barred Beatdown on Tom.
Boom, Headshot: The Mafia frequently mentions shooting a person "in the brain" and it is how Mink, Bernie, and the Dane all die.
Bottomless Magazines: Leo fires a few thousand rounds from a Tommy gun without reloading. Rule of Cool is in full effect there, since it takes about 5 seconds of continous fire to empty a Thompson machine gun
Brother-Sister Incest: Bernie claims that Verna once tried to "cure" Bernie's homosexuality herself, though his word is less than trustworthy.
Bury Your Gays: Bernie, the Dane, and Mink are all dead before the credits roll, although they're not the only casualties.
In addition to the Sam Raimi example below, frequent Coens collaborator (and wife of Joel) Frances McDormand appears as the Mayor's secretary.
Catch Phrase: Tom's "I'll think about it", which he says whenever he has no intention of doing what's been asked of him. Casper is smart enough to realise this, and so has his thugs beat Tom up when he tries the line on him.
The Farmer And The Viper: Lampshaded by Bernie, who claims, while pleading for his life, that ripping people off is just "his nature". He demonstrates it when Tom spares him and Bernie immediately blackmails him for disobeying the order to kill him.
Femme Fatale: Verna, subverted. While plenty of people die because of her, she's not directly responsible for any of them, even the one Tom blamed her for. She's the only person in the movie who genuinely doesn't want anyone to die, but her affair with Tom and her love for her brother get everyone else killed. She's a Femme Fatale despite her best efforts.
Actually, this one is kind of double-subverted, in that the character who plays the Femme Fatale character type much more closely is not even a woman...it's Verna's brother, Bernie (maybe an alternate definition for "femme")
Homoerotic Subtext: Tons on it. Notably, a lot of Tom and Leo's dialogue makes them sound like a couple, and the Tom/Verna/Leo Love Triangle is arguably more about Tom and Verna competing for Leo's attention than Tom and Leo competing for Verna's. And then there's Bernie/Mink and Eddie Dane/Mink, but those are more text than Subtext.
The local police chief affably chats up Tom both times. Once when his cops are helping the Irish mob take out members of the Italians, and again when the power shifts to the Italians and the cops take out the Irish mob instead.
When Tom hits the Giant Mook who's about to beat him up across the face with a chair, the latter says plaintively "Jesus, Tom!" like his feelings rather than his face have been hurt.
Idiot Ball: Frankie and Tic-Tac are given orders to make sure Tom kills Bernie. So what do they do? They stand by the car and wait while Tom walks Bernie into the woods. Alone. This is later lampshaded by the Dane, who beats them both up for being stupid and goes to check for a body.
Jerkass Has a Point: Tom is arguably a jerk towards everyone because of his bluntness; nevertheless, he is right about everything he warns Leo about and has to weasel himself out of the mess when Leo ignores him.
Dane is a murderous psycho alright, but he is right about everything regarding Tom, but he's two steps behind.
Bernie plays Tom out of murdering him and blackmails him just because Tom exposed himself by doing so.
Kick the Dog: The movie's full of them. Leo delights in screwing with Johnny just because he can (he claims it's to protect Verna, but the sheer joy in his voice after says otherwise). Bernie does it when he kills his boyfriend to cover his own death. The king of it all, though, is when Johnny Caspar is killed right outside Tom's apartment. It's meaningless, since Leo can take care of the police.
Kick the Son of a Bitch: By the near end of the movie, Tom, when he kills Bernie. At that point, Leo's solidly in power once more, and both Tom and Verna are safe, and Bernie no longer represents any threat to Tom. The reason it technically fits here instead of Kick the Dog is because, Tom's previously shown not to hold grudges with his bookie's muscle, and kills Bernie without a hint of passion, so it's not revenge. Tom kills Bernie simply because he doesn't like the little weasel. Of course, this backfires for him, unless he'd made peace with the fact he wasn't going to end up with Verna, because it's obvious at the end that she knows.
Caspar: "Just like I tell all my boys...ALWAYS PUT ONE IN THE BRAAAAAAIIIINN!"
Life Imitates Art: The Coens found it first hilarious, then infuriating, that while filming this movie full of police corruption they were repeatedly hit up for bribes by New Orleans Police Department officers.
Loan Shark: Lazarre and his underlings are Affably Evil ones. His stooges feel free to rough up the right-hand man of the city boss, but only a little bit, and not breaking anything. They know Tom personally, they're sorry about doing what needs to be done, and advise Tom to stop borrowing so much when he's already in debt.
Mood Whiplash: After the mostly comedic first half, the eponymous "Miller's Crossing" scene is pretty jarring.
More Dakka: During the siege of a Bad Guy Bar, dozens of cops and mobster all fire their pistols at the club and one of them even unveils a water-cooled Browning M1917 machine gun. Also Leo unloading his Thompson.
A newspaper headline seen briefly reads "Seven Dead in Hotel Fire". This is a reference to Barton Fink, which was released a year later than Miller's Crossing but written at the same time. Also, Tom's apartment is at the 'Barton Arms'.
The opening scene is also something of a parodic parallel to the opening of the original Godfather, where an Italian man gives a monologue to a mob boss, requesting a murder.
Several nods to The Third Man, particularly the ending and many camera angles.
Shovel Strike: Johnny Casper viciously does this to the Dane when he is manipulatied into thinking that the Dane is a traitor.
Too Clever by Half: The Dane's evaluation of Tom. Zigzagged as Tom's schemes are about to backfire on him, but this gets subverted by dumb luck thanks to a second body disposed in the woods
The Dane You are so goddamn smart. Except you ain't
Very Punchable Man: Tom is a rare (maybe unique) main character variant. He commits two overt acts of violence in the movie (hitting a Mook with a chair and killing Bernie). The rest of the time he's getting his ass kicked left and right — often by design.
Zero Approval Gambit: Tom deliberately alienates himself from Leo (and takes quite a few beatings in the process) in order to eliminate Leo's competition and any threats to Verna while simultaneously providing himself an exit from his life of crime. This comes at the prize of losing Verna to Leo.