When one's book sells, does one send a gift to their agent and/or editor?  If so, what might they send?

I have some ideas, but maybe they might be cheesy.  And also, if it isn't something that's generally done, I don't want to be a dork and send  a gift.  If it is something most people do, I don't want to NOT do it and be clueless and faux-pas committing!