Nobody's too old for anything, honestly. If you think you're going to get laughed at, though, you're just going to exert some inner strength... you matter most and you shouldn't be restricted from doing what YOU want, just because of sterotypes!
I find sterotypes the most rotten things ever. Some sterotypes put people down. People at school are sexist and the boys always seem to make out that girls are not as sporty as boys. My friend asked me why I read Deltora Quest, because according to her, "those books are for boys" because a lot of boys like to read Deltora Quest. The Tamagotchi ads that I've seen on the Internet show a lot of girls (but the v4 one DOES show a boy in it) and Tamagotchi nowadays are pretty overloaded with games (let's match the shapes! let's play the claw game!) so perhaps that's why people consider Tamagotchi "little girly toys." Don't let that stop you though.
I consider the fact that I still wear my Tamagotchi 'round my neck a sign of, well, toughness. I've been teased over and over again. I just ignore it. Does it really matter that almost nobody has one? So what. I'm unique. Do I have to stick with what's really "in" and "popular"? I'm not the type to watch music videos on the Internet, go see movies or play Knock 'n' Run (you know that game where you knock on people's doors, then run for your life?). I might look like an outcast, but who really cares.
Ramble over.