I would sell them. If it was meant as a gift, I would still like to get something out of it, lol. Besides, the more I learn about places such as GoodWill and how they treat their employees, the less inclined I am to give to them anymore (they take advantage of loopholes in the law which allow them to pay disabled workers far below minimum wage and take advantage of them). Same goes for the Salvation Army (they routinely discriminate against gay people).
My family doesn't celebrate christmas, but we do exchange gifts during some holidays. When they give me something I really don't like, I just say thank you and smile. I keep the gift, if it's something that must be worn... I just throw it into the closet and odds are I'll never see it again But yeah, in general I keep things!
I don't usually receive Christmas gifts, which I will be so lucky if I do. I normally receive gift cards and post cards, which I will use up the gift cards at the store and keep the post cards in my room. There was a year in which I received a tablet for Christmas, which I sold it because I didn't really need it.