This thread is sort of like the "Most Kerbal thing you have seen in real life" thread, just in KSP. It would probably have to be turning a Kania truck into a rocket. It was just for fun and I think I used infinite fuel to get it to space, but that's what the kerbals are about, right? Honestly, I haven't done that much kerbal-y stuff in KSP. I haven't really been to space that much. I'll put pictures of the truck here soon.
EDIT: I just made a helicopter version that actually (pretty much) works. Now I am working on a truck/plane!
ANOTHER EDIT: The plane worked ok, and I landed successfully, besides that I lost part of an engine during the landing. It only happened because I have the wheel brakes set too strong and the truck turned and rolled a little as it came to a stop.