Late to the party, I picked up one of these just for the heck of it: de45
It doesn't like tall grass, because it gets lifted off the ground, but its been great in dirt and rocks.
I've used it rock crawling at the beach, and set up an obstacle course on my deck, that I can drive round while I'm in meetings.

It's not "good", wide turning radius, only one speed, but for the price of a used video game I'm having a blast.