The One Where They're Up All Night - S7-E12
Continuity mistake: There is a long shot of Rachel and another person sitting on the sofa and Rachel's wine glass is almost empty. She then goes over to the the counter to fill it up. However, before she starts to fill it, a significant quantity of wine can be seen in the glass. (00:07:35)
Answer: Usually by the seventh night of Hanukkah you don't know what to get the other person, and you will probably resort to getting the other person something insignificant. Chandler is basically saying that the pen is a stupid gift.