Helter Skelter and On the Track are pretty easy, but they're all over played.
A good thing to do is take a well known solo and add a bit of improvisation over the top, put in a few extra glisses and stuff. A bit of artistic licence always goes down well with an audience.
Have a listen to Evelyn Glennie's "Reflected in Brass", there's a few nice solos on there, as well as arrangements for marimba and vibraphone.
Most of them are pretty easy, i dont know if she'll have the only rights to the music though.....