Are there any aircraft with powered landing gear? My student asked me a question this morning.  It was:


  A car drives by turning its wheels against the Earth. An airplane taxis by rolling on its wheels while the engines push against the air.  Are there any airplanes that taxi by turning their wheels, like a car?


I assume the answer is no for reasons of weight, complexity, and so on, but it's dangerous to say never.  Are there in fact any airplanes that fit her description?

Edits in response to comments: 


She was thinking of "normal" airplanes, not airplane/car hybrids.  
Peter Kämpf's link is the kind of thing she was thinking of.
WheelTug makes an addon motor for a nose wheel. This is a demo of the unit being developed for a B737. They intend to lease it to airlines. It works well under most circumstances, but has difficulty on icy aprons and the aircraft would need a pushback so it could taxi using its engines. The terms of the lease would financially compensate. They have "reservations" for 1100 units from two dozen airlines.


youtube

There are a number of financial considerations, such as cost to carry the weight of the unit. Here is a presentation of their business case. They claim direct cost savings similar in value to installation of winglets, and time savings value twice as great as replacing a current generation 737/320 with a Max/Neo. 


youtube

Safran also had a joint venture to develop a similar unit for aircraft maingear, but that is no longer being pursued. I don't know of any OEM that offers this kind of capability on commercial aircraft.