Sigh. I keep it. I make a point of wearing it around them once or twice. I talk more about other fragrances that I love as well, and suggest they try them.
I make blind buys myself, so in the long run I don't want to discourage anyone from gifting me with fragrance. If I find someone who likes the present, I offer it to them, saying it was a gift but I can't appreciate it, and it needs a loving home.
The benefit is that once, I really did fall in love with a sad little fragrance called Paris.
(Thank you, Robin.)