The Thief Acrobat seems like a great combination between a rouge and a gymnast.
It's designed as a 20 level class, but includes prereqs if you like the idea of making it a prestige class. It keeps the basics of a rogue, with the sneaky nature, but adds in quite a few good abilities for movement in both combat and adventuring.
Two things I really like: Thief Acrobat Talents, which allow for a good deal of customization. The other is a nice section on how a Thief Acrobat can make money on the side doing gymnastic style performances.
Well worth the small amount of money being asked for.
