I have been playing ksp for quite a while now, mostly building mediocre tanks and planes, but recently I created a very silly and surprisingly useful land vehicle. It's powered only by reaction wheels. On it's ends I added wheels and landing legs (for safe spinning on the side and jumping) and also enough RTGs to power it even at full speed.
Specs:
Part count: 50
Top safe speed: 25m/s
Torque: 80
Mods used: Kerbal foundries
link: https://kerbalx.com/samuel9900/Spiny