Every theme available, free or premium, will work with bbPress because bbPress is made to work with any theme through the theme compatibility layer.
bbPress is made to work with any theme, and in most cases, it will look the same with every theme. Still, bbPress styling and templates can be fully customized, and here are the 5 best looking premium themes that vastly improve how bbPress looks like.
You can see the larger portion of the preview image, by scrolling each image vertically.
All prices are subject to change, and for the latest price, check the theme websites.