A: George to the AA sponsor

Q: "Do me a favor will you? Take the pen and the scotch tape and get the hell out of here!"

A: Morty to Jack
Q: It's all pipes. What's the difference!?

A: George to Jerry & Elaine

Q: "So you're so grateful to have sex, you'll just shout out anything that comes into your head?"

A: Jerry to George.

Q: Das cafes por favore, y un ensalada grande...Ahh, don't mention it."

George to the waitress

"...he is known, as the comedian."

A: Jerry's girlfriend the gymnast to Jerry

Q: "He's a jokemaker."

A: Kramer to Brody
Q: It's Risk. It's a game of world domination being played by two guys who can barely run their own lives

A: Jerry to Elaine

Q: I know this doesn't seem like work, but if you wouldn't mind conducting the lunatic convention down the hall...

A: Jerry to his and George's Parents.

Q: "What about Sharon Besser?"

George to Jerry

"Sometimes."

^^^ Thats a little vague there, pal.
Mind posting one thats a little more specific?

Easy one- "Sex...to save the friendship? "

A: Jerry to Elaine.

Q: "Hey Jurrry. You know sometimes...?"

A: Jerry's girlfriend who doesn't respect his being a comedian on Jerry's answering machine.

Q: "I can't believe I'm saying this, but that's not a bad idea."

Jerry to Cosmo

"Did I tell you to put the balm on?"

Jackie Chiles to Kramer
"Where'd a nice kid like you learn such a bad word?"

A: Mickey to the little kid who said Kramer (dressed as Santa) was a Communist.

Q: "Don't be ridiculous. Now, if you'll excuse me, I have to go fill my freezer with my own blood."

Kramer to Elaine

"I had a pony"

Jerry's old relative about her days in Poland.

I invented 'it's not you, it's me!'

A: George to his ex-girlfriend Gwyn

Q: "Why don't you go on your three hour break?"

A: Newman to Violet
Q: I heard he used to polish off a box of Triscuits. Oh yeah, Gandhi loved Triscuits

A: Jerry to Elaine

Q: "I'm a man who respects a good coma."

A: Jerry to Gina
Q: Well, there's always a place for you on our team

A: Jerry to Elaine.

Q: "When they like me, I don't like them. When I like them, they don't like me."

Could be two answers: either George to Jerry or the two old men who they volunteer to help in the same episode.

Q: "Have you ever worn a fake beard?"

Kramer to Jerry

"You already have an in, you have the same first name."

A: George to Jerry re: meeting Jerry Lee Lewis

Q: "Because I gotta intimidate when I'm on the mound. Well the next pitch, he's right back in the same place. So, I had to plunk him."

A: Kramer to Jerry
Q: All these big companies, they write off everything

Kramer to Jerry re. the Post Office
"He's 9 years old! You dont need karate. You can just ring his neck.":

A: Jerry to Kramer
Q: Poise counts