I’m kind of partial to the steam ones, as stupidest of all, but you take your pick —
https://youtu.be/Fub8QAE26Zg
50 more “What-The-Hell-Is-That” motorcycles —
https://youtu.be/E_yCy0vJQjg
Still more, but not in the “Stupid” category; more in the extreme category —
https://youtu.be/0aOG4nTLXZ4
Then, the pièce de résistance —
https://youtu.be/rKQ5f8tvRxY