The one that's made the most recent addition to our repertoire is "I'm not here to help you." Or, if we're feeling like being more obscure, "You must not have seen my business card."
[One of our players introduced us to the cancelled but surprisingly not terrible series "Miracles" (a much better show than its ad campaign and lackluster network support would indicate), where at one point the main character is admonished "We aren't here to help people," and he fires back with "Maybe we should put that on our business cards: 'WE ARE NOT HERE TO HELP YOU.'"]
Beyond that, we've got the old favorites:
"Think short-term" as the default reminder to people to use whatever charged items, one-shot items, or limited resources they've got NOW because losing means you'll never use them at all.
"How about the brick?" or "What if we crash a dump truck full of manure into a busload of prostitutes?" whenever people get sidetracked by a long what-if scenario while making plans, both from previous games where we wasted hours arguing over increasingly dumber options.
"Read your hand" or "You should write that on your hand" when people forget about one of their character's powers, from our last D&D game where the air genasi remembered one session too late that when he was trying to climb that wall and failed, he could have just levitated up there instead. That game was full of players holding one hand theatrically in front of their face and pretending to read something like "I-don't-breathe" or "I-can-turn-undead" slowly and methodically.
"It's soooooo saaaaaad," delivered in a high-pitched, sing-song voice whenever a great tragedy has been revealed.
"He's DREAMY..." whenever an NPC opponent is determined to be attractive to a PC. This was the most fun in a 7th Sea game where our Vodacce witch had the flaw of always being attracted to the wrong man.
"I sit in my dinghy," whenever you're holding an action. This isn't even ours, it's from an old Champions story we found on the net from a game where every hero except the Texan gunslinger could breathe underwater. Everyone else was duking it out below the waves, and each round the gunslinger's player would announce in a loud Texas drawl, "Ah sit in mah dingy and ah hold mah action."
"Don't taunt the bad guys," when the aforementioned bad guys then turn around and kick someone's ass really thoroughly. This comment is always followed by indignant complaints from the players who were taunting the bad guys, who usually add "Also, taunting worked really well that time we...uh...well, it helped when those guys....um....look, it's just FUN, okay?!" at the end.
"NPC dice" are what we call whatever the GM is rolling, if the rolls are really bad. Whenever the GM is rolling well, someone begs: "Please, use the NPC dice instead!"
And a few phrases I like have, sadly, fallen out of use:
"Way to notice things, Captain Noticey McNoticerson of the 'Look!' brigade," when someone just went all Captain Obvious on the group or when the party's Perception Whore rolls really badly. Took a long time to say, but lots of fun.
"INDEED!" when agreeing with an NPC, either delivered in the style of David Lo Pan from the movie "Big Trouble in Little China" or in the nasal style of Lord British from the opening movie to Ultima VII Part 2. (If the latter, you usually add "PUT IT ON THE TABLE.") Or sometimes you might say it like The Tick. Very versatile, but it ended up being overused.
"Quiz dice" and "Query dice" were the old way of referring to the NPC dice phenomenon, from a Gotham City game we played (using the Adventure! rules) where one of the Riddler's sidekicks, Quiz, kept rolling absurdly well while the other, Query, kept botching. Not enough of us were playing in that game for this to really establish itself.
--
obviously, we're a very in-joke and catchphrase-loving group
ryan