Here are my favorites;

Chandler - "Can open... worms everywhere"

Rachel - "You fell asleep!?"

Ross - "I grew up in a house with Monica, okay. If you didn't eat fast, you didn't eat."

Joey - "It's like a cow's opinion. It just doesn't matter. It's moo.

Monica - "Guys can fake it? Unbelievable! The one thing that's ours!"

Phoebe - "When I was in Junior High School I went through this period where I thought I was a witch. And there was this guidance counselor who said something to me, that I think will help you a lot. He said okay, 'you're not a witch you're just an average student.' See what I'm saying?"