Here are mine (some of these are paraphrased):

Maria: "Mr. Moore, we appreciate everything you've done for us. You got us to go to dances, you got us to play volleyball, you got us to make a rock video...but you've done enough. Leave us alone!" (I want to say this is "The Write Stuff," but I gotta look it up on tape.)

Dennis: "Remember the word 'trust'?"
Jawaharlal: "Remember the word 'sucker'?"
("Crimes of the Heart")

Mr. Moore: "Janice, have you been sending me love letters?"
Janice: "Barf-o-rama!!"
("Love at First Byte")

Dennis: "Jawaharlal, now that you're on the Indian Layaway Program, were you still interested in a computer match?"
Jawaharlal: "Sure, why not. I mean, how can you cheat on a five-year-old?"
("Don't Play With Matches")

There are more, but I'll post them when I remember them.

Those were fun to read, keep them coming!

Dr. Samuels: (barging into the IHP class) "I have great news. I just got off the phone---"
Charlie: (sarcastically) "That is good news!"
("Video Activity," I think.)

Dr. Samuels, 100% positive that Charlie won't pass the Macro Economics test, tells Charlie a racy secret about role playing as the Big Bad Wolf (w/Mrs. Samuels as Little Red Riding Hood). Charlie thinks that it'll come back to haunt Dr. Samuels, but Dr. Samuels thinks otherwise. Of course, Charlie passes the test, and can keep his license to teach. As soon as he sees Dr. Samuels after the good news:
Charlie: (like a wolf) AAAAAAAAAAAAA-WWWOOOOOOOOOO!
("Past Imperfect")

A ton of girls for Peer Counseling approach Eric in the hall to verify their peer counseling appts. with him. Charlie questions him, and Eric tells him how it's for peer counseling and that there are so many "needy girls" out there.
Simone: "Maybe we should cancel our date for this weekend. You'll probably be too busy---HELPING THE NEEDY!"
One of the moments that Simone breaks out of that "shy, quiet" character of hers.
("Let's Rap")