For Trek-geek squee, one moment that's always stuck with me from the DS9 premier episode:
I'm sorry... have we met?
Yes, sir. We met in battle. I was on the Saratoga
at Wolf Three. Five. Nine.
(I wasn't big into Avery Brooks at times, but the delivery of that line was spot on.)
From TOS: Any part of the exchange from "This Side of Paradise" that starts with Kirk saying "Alright you mutinous, disloyal, computerized half-breed, we'll see about you deserting my ship."
Or from "The Trouble With Tribbles," when the director of DS-7 accuses Captain Kirk of taking his mission lightly, and Kirk replies "No sir, I take the mission very seriously, it's you I take lightly."
(Sounds dickish, but the guy deserved it.)