I just reread the "Hanners and Sven go on a date" ark from the 1750ies onward. One of my favourite QC moments (though not really a single quote) is definitely in there:
http://www.questionablecontent.net/view.php?comic=1760 Hanners: Could you explain how, exactly, Sven would "seduce" me?
Faye: Okay, here goes. First he takes you shopping at that store with all the cute little organizational bullshit and buys you whatever you want. Then you eat at that vegan café that wins "Cleanest Dining in the Valley" every year. After dinner, you go back to your place, where you watch a movie about fonts he rented. When the movie ends, he turns to you, looks deep into your eyes... and offers to clean your kitchen."
Hanners (blushing): Th-that wouldn't work.
This is so great!
(I hope I didn't overlook it mentioned before... I read this entire thread some time, but it's been a while.)