What is the best thing to do with a gift someone gave you but you don't really have a use for?

If they wouldn't find out, you could re-gift it to someone else. Some people find that idea unpalatable, but I think making use of something while at the same time making someone happy is a far better use of the item than stashing it in a closet. If the friend would find out you've given the gift to someone else, the best bet is to be gracious and simply use or store the gift. Send it to the Salvation Army, the Red Cross or some similr charity. They will find use for it or sell it and use the money to help the needy. Don't just trash it, and never 're-gift'.