There are so, so many...over 30 years or so we've accumulated a massive pile of quotes. Here's a few just from the current batch that haven't been typed up yet:
"Let's go get killed!" - a player OOC, trying out a new party battlecry
"By the time we get this session over, 6th edition will have been released." - another player OOC at the start of what looked like a long and messy in-party trial.
"We had so many horseshoes up so many of our orifices!" - a player OOC telling the tale of a battle the party was very lucky to survive.
"Where the hell are we?" - Chembri, a War Cleric, party is plane-hopping
"That might be exactly where you are." - me as DM
"Then that might not be a good question." - Chembri's player.
"If I die, cure me quickly!" - Zxancs, a fighter, to the aforementioned Chembri
"It's either I die or the quest kills me." - Zxancs again, the eternal optimist
"I'm insulted that you dismissed my non-existent suggestion that I didn't make." - Chembri to Zxancs.
"I was just trying to find out how incompetent I am." - Ymet're the wisdom-6 MU fumbles with a weapon
"Well you're doing it wrong." - Kit, a fighter
"What is the striptease value of a buckler?" - a player equips a new PC
Lanefan