Something well out of my comfort-zone, built for the 100th Lugnuts challenge. This is a vehicle from a video game called Twisted Metal.
Warthog (2) by Duq, on Flickr
It's got a full set of Power Functions inside, and steering is done with an adder/subtracter mechanism rather than simply one motor for each side.
Warthog (5) by Duq, on Flickr