I love "TOW the Joke" where Monica asks Phoebe and Rachel who among them they'd pick to date and Phoebe picks Rachel, since Monica is too high maintenance.
My favorite part is when Chandler (after reciting a speech prepared by Monica about how she's not high maintenance) finally admits that Monica is a little high maintenance, but then says to her, "So they can say that you're high maintenance, but it's okay because...I like maintaining...you."