[Woolly]

We have one, based off of a motorized wheelchair, and an added scissor lift on the robot platform so that we can work on certain things more easily.
We've never had a safety issue with running people over, in part because we still yell "ROBOT", and because of all the flashing lights we have on it.
Though, of course, we still have a manual cart as a backup, and for carrying other heavy things like parts, batteries, and etc.
But yeah, we haven't seen anyone else that has a motorized cart, I kind of feel bad for the people who have to pull theirs everywhere.

I actually don't have any pictures at the moment, but It's pretty sweet.