Any time Campbell has to report in to his boss: Winston Churchill. Watching cool, collected, ruthless Campbell stammer and ramble like a schoolboy is hilarious.
Polly losing her temper with Tommy in the church in 1.01, smacking him repeatedly and yelling at him.
John's double-take as he figures out Finn's drunk his beer at the bonfire. Finn's ten.
Polly's "Shut Up" Kiss to Campbell, to psych him out after he starts interrogating her and manhandling her.
Ada being five weeks late in her period. Seven, if you count weekends.
Tommy Shelby on clothes shopping: "My suits are on the house, or the house burns down."
Tommy's one-word response to the IRA sympathizer's Nightmare Fuel singing and general craziness: "Bravo."
Freddie and Polly's exchange in 1x03:
Freddie: You think I can't handle Tommy Shelby?
Polly: I know you can't. I'm having trouble these days, and I'm twice the man you are.
Tommy gets Polly back later in the episode, also while speaking to Freddie: (on the subject of Polly attempting to pay off Freddie to leave Birmingham) "Polly must have had a rush of blood - or port wine."
Arthur's sartorial commentary to Grace at Cheltenham, while he's in the middle of a robbery: "Nice dress."
The entire scene where poor John tries to convince the rest of the family he should marry Lizzie Stark. Arthur's snickering into his drink, Polly's making hooker wisecracks, and even Tommy's hiding smiles behind John's back. All of Polly in that scene, really.
John: I want you to see how brave she is!
Polly: Brave is going where no man's gone before . . . and with Lizzie Stark, John, that is really not what you'll be doing.
Polly: Men and their cocks never cease to amaze me. John, Lizzie Stark's never done a day's work vertical!
Grace saying she's Irish, she knows a million toasts.
Tommy informing John he's getting married . . . standing in front of the gun-wielding Lee family and telling John to "smile, it's a wedding".
Tommy and Campbell talking about a potential team-up. The dialogue is great (and surprisingly full of Ho Yay), but the capper is Campbell's amused smirk at Tommy's response.
Campbell: If I win a medal, I will have your initials engraved on its back side.
Tommy: My initials on your backside? Quite an image.
Tommy: (completely unsympathetically) Yeah. Just when things are starting to go right, Arthur, you've gotta go and do this? Look, youíre one of three shareholders. Me, you and John, and according to the law, we are equal partners and itís written on the paperwork in black and white. A third, a third, a third. But the thing is, well, me and John, we quite fancy splitting your share so, just next time, use a gun, man.
Tommy bursting in on John and Esme's "efforts in cooperation".
Tommy: John, I've told you to keep the doors locked. Could've been anyone. Get dressed, we're doing it today.
Esme: Bugger that, he's doing me today.
Tommy: Yeah, well, make sure he's done you by nine.
Mr. Zhang's laundry service also boasts a brothel, and he'll clean and press your shirt while you're busy with your hooker.
Winston Churchill's offhanded mention that the Prime Minister doesn't smile unless a political opponent dies.
As Ada shows off her new baby, Arthur steals him and puts his razorblade cap on the baby's head.
Arthur: Look, he looks just like me!
John': That's his arse looks like you, Arthur.
Jeremiah deciding to join the battle.
Tommy: I know you've vowed never to pick up a rifle again, Jeremiah, but can you ask God from me if you can help us today?
Jeremiah: God says he don't deal with Small Heath, sir!
Ada walking into no man's land between the Peaky Blinders and Kimber's men - pushing her baby carriage and ordering her husband to shut up.