Tony Stark: What's the vibranium for?
Ultron: I'm glad you asked that, because I wanted to take this time to explain my evil plan.
James Rhodes: Think I can’t hold my own?
Tony Stark: We get through this, I’ll hold your own.
James Rhodes: You had to make it weird.
Ultron: You're incredibly naive.
Vision: Well, I was born yesterday.
Maria Hill: All set up, boss.
Tony Stark: Actually [points to Cap] he's the boss. I just pay for everything and design everything, make everyone look cooler.
Iron Man: [After incapacitating a room full of bad guys] Good talk.
Crippled thug: [Whimpering] No it wasn't.
Hawkeye: Are you up for this? Are you? Look, I just need to know because the city is, is flying. Okay, look, the city is flying, we're fighting an army of robots, and I have a bow and arrow. None of this makes sense.
Tony Stark: Please be secret door. Please be secret door. Please be secret door. [Finds secret door] Yay!
Captain America: You get hurt, hurt 'em back. You get killed...walk it off.
S.H.I.E.L.D. Officer: Number six boat is topped and locked...or, uh...or stocked, topped...it's uh, full of people.
Nick Fury: Guy’s multiplying faster than a Catholic rabbit.
Natasha Romanoff: [Talking about Hawkeye] Are you sure he’s going to be OK? Pretending to need this guy really brings the team together.
Ultron: I know you're good people. I know you mean well. But you just didn't think it through. There is only one path to peace... Your extinction.
Ultron: You think you're saving anyone? I turn that key and drop this rock a little early and it's still billions dead. Even you can't stop that.
Thor: I am Thor, son of Odin, and long as there is life in my breast...I am running out of things to say. Are you ready?
[Vision sucker punches Ultron with Thor's hammer.]
Vision: It's terribly well-balanced.
Thor: Well, if there's too much weight, you lose power on the swing.
Maria Hill: He’s fast and she’s weird.
Ultron: Everyone creates the thing they dread.
Tony Stark: [Mid-battle with Hulk.] Hit me in the back?! Dick move, Banner.
Tony Stark: You listening? That little witch is messing with your mind. You're stronger than her. You're smarter than her. You're Bruce Banner.
[Hulk roars angrily.]
Tony Stark: Right, right, right. Don't mention puny Banner.
Natasha Romanoff: Thor, report on the Hulk.
Thor: The gates of Hel are filled with the screams of his victims!
[Natasha glares at him while Bruce groans and puts his head in his hands.] Thor: But not the screams of the dead, of course. No, no... Wounded screams... Mainly whimpering, a great deal of complaining and tales of sprained deltoids and...gout.
Chosen answer: This is a fairly US-centric gag. In Archie comics, the titular Archie has two competing love interests: Betty and Veronica. Given the Hulk/Banner's history with Betty Ross being able to calm him down, Tony Stark has named the containment system/Hulkbuster armor "Veronica".