What is the single greatest line in television history? {Please include context & Episode of the Series}

Makes for an interesting trivia question, although the answer will be obvious now.

Steven Zirnkilton has been on prime time, network TV every week for 36 years. What role does he play? (He does the voiceovers at the beginning of Law & Order, and its various spinoffs.)

From the last episode of Coupling

      Yeah, trust me, the word wasn’t “can’t”.

Context (bear in mind, this is a London British accent):
Susan is in labor. It is not going so well. Steve comes flung out of her hospital room and explains to the nurse that he is supposed to ask her two more times if she really wants an epidural.
Nurse: She said you can’t.