Aww that's sad :( What a cute item! It's always more special when something has sentimental value.
My favourite is my old Ivysaur keychain. It was the first Pokemon merchandise I ever got, along with a Pikachu from the same set.
I used to take them to school everyday, and my friends would pass them around and have turns "taking care of them" during lessons. xD Sadly someone broke my Pikachu's tail off and Ivysaur is scuffed from being carted around. D: But I guess it gives them character. I still take Ivysaur with me as a kind of good luck charm if I'm nervous about something!
My less sentimental favourites would be my walky Bulbasaur
plush (I think it's the cutest Bulbasaur plush ever :D) and my giant Bulbasaur
(It's almost real sized!).