"Fascinating". One of Spock's favorite words.
"No tribble at all". Famous phrase uttered by Scotty.
"Make it so". Famous phrase uttered by Captain Picard.
"Temporal anomaly". Used in various Star Trek series, probably most often in Voyager. It's a good answer when you've got time issues. "Sorry, I'm suffering from a temporal anomaly!"
"Lay in a course, to/heading..." Said by numerous Star Trek captains. It's probably used by captains of naval vessels, but if anyone ever says it I instantly think of a Starfleet captain giving orders to the navigator.
"Food replicator". I used to work with a guy that referred to the vending machines as food replicators. Yeah, it definitely over-branded him as a Star Trek nerd. I used to remind him that they are food "dispensers" not replicators, but he refused to listen.
"Gundun." Phonetic for "GNDN", the term used for various conduit props on Star Trek sets. "Goes Nowhere, Does Nothing." Useful to describe useless employees at work. "Jim? Oh, he's a gundun. I don't know what the hell he does and he's always sitting there. I guess he's just paid to show up."