Lego Technic is perfect for creating quick prototypes of pretty much anything, combine this with RC stuff and you can create really fun stuff. One simple example is the robot i describe in this post:
Sunday afternoon robot

My old Lego is usually stuffed away in a box in the basement, but when we have kids visiting we usually bring it up to the apartment. I suspect I’m the one enjoying it most and this time I built a RC lego car

From the side

The motor and propeller us used as a pusher

The battery, ESC and receiver is secured with a rubber band

I use a HXT900 servo to steer

After a few testruns I added a propeller protection bar to minimize the risk of running into something with the propeller.

Propeller protection

Runs great, I’ll probably update this post with a video when I’ve recorded one.