I am presently using a modified Traxxas E-Maxx chassis which is a bit pricey.
Others have used a 1/8th scale RC Rock Crawler, the Redcat Rockslide, like John Arne Birkeland's Rover1: http://diydrones.com/profiles/blogs/crawler1-land-based-rover
Hope this helps!
Any hobby RC vehicle made should meet your requirements ;)
What kind of terrain? What's the intended straight line and cornering speeds? What's your budget? What other requirements could help narrow down the choices?
I used an ECX Circuit 1/10th scale stadium truck because I had a low budget (it cost ~$130), and wanted something reasonably quick (25mph range), with decent pavement handling but enough clearance to handle 1-2" bumps and potholes.