You should either keep it, like SailorRosette said, or sell it.
I personally wouldn't give it away to someone, I made the bad choice of giving friends about 6 or so of my unused Tamagotchi's thinking that we'd be playing with them for years(which I did) but sadly, they stopped playing with them in about a month. Im guessing they dont even have them anymore or just lost them.
I could have kept them as a keepsake and maybe even started a collection.
So pretty much my point is, if you decide to give it away to someone, make sure it's someone who's a true Tamagotchi fan and not someone who says "Oh yeah I like Tamagotchis..."