OK mine started out as worst gift ever, but turned out to be cool.
When I was like 14 or so, my cousin's Grandma (who we always celebrated holidays with) gave me this styrofoam wreath shape with multicolored Christmas ball ornaments hot-glued all over the front of it. It was so ugly, I was like but, to be polite I just said thanks, and set it aside.
Everyone kept asking me if I liked it, and things like "Oh that was so nice of her." I thought they must be crazy or something. Finally, someone mentioned to me that I might want to pull the top part off of one of the balls, and inside each ball was a $1, 5, or 10 bill! I made out like a bandit and felt like a total moron.