The One With Phoebe's Rats - S9-E12
Continuity mistake: When Gavin and Rachel are in Rachel's office, in some shots Gavin is wearing a wedding ring. (00:03:43)
The One With Phoebe's Rats - S9-E12
Continuity mistake: At the party, when Monica and Rachel are talking about Gavin, Rachel has a napkin in her hand at one shot, the shot changes and the napkin is replaced by a drink. (00:13:20)
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.