How do I say no to a present?

I have a feeling that I’m going to be getting a present for the holidays that I don’t want. I don’t want to appear ungrateful (is that a word?) but I don’t want my pop spending his money on something I won’t be using. Two things I’d rather not do: return it in exchange for something else, and/or ask for something else: I don’t really want much of anything, anyway! So, what’s the best tactic? Thanks!