Ace putting his pants on in his office before a meeting with the County Commissioner.
Nicky escorting a gorgeous showgirl out to his car to get a blowjob from her while, all the time, droning on about the veal he stocks in the kitchens of the restaurant he owns.
Nicky's constant over-the-top cursing and insults often crosses the line into hilarious. The funniest one is his berating of the guy who who took his shoes off and put his feet on the table at Ace's casino:
Piscano's mother's face when he says, "They could all be in on it together, those miserable fucks!"
"I'm sorry, Ma, I'm sorry, I'm just, I'm upset!"
This could well be a result of - it' s not really a trope but I think you'll understand what I mean - accidental method acting. The actress playing Piscano's mother is Martin Scorsese's mother, who at the time was slowly starting to show symptoms of Alzheimer's disease. Guess it's a real life example of a "Funny Aneurysm" Moment.
Ace's daughter endlessly antagonizing Lester and driving him nuts.
"She started it. She started the whole thing. I'm just standing here."
At the end, following a confrontation between Ginger, Ace and Nicky, Ace ends up paranoid that he's going to be receiving a visit from Nicky and his friends that he won't survive. The next morning, having stayed awake all night with Billy and a shotgun, he hears a noise on the lawn. It's Ginger, drunk and high, repeatedly driving her car right into the back of his and screaming at him. The look on Ace's face is part relief, part "... Really? I stayed up all night for this?"
Ace's Control Freak nature hits overdrive when in the middle of his tense life, he notices that his blueberry muffin has fewer blueberries than that of the other guy's plate. So he marches down in to the kitchen and tells the kitchen staff to ensure that there are an equal number of blueberries in each muffin. When the chef tells him that this will delay cooking, his reply is one for the ages.
"I want an equal number of blueberries in each muffin. I don't care how long it takes."