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