Like any of us, car designers sometimes need to let off steam. But while you or I might do so by hitting the gym or downing a quart of rum and backlogging the office photocopier with 100 pictures of our butt, these guys get to let their hair down on the job. Bored of churning out endless schematics for an efficient, economic family car? Take time out to design a nuclear-powered Ford, or a roadworthy UFO. OK, it doesn’t quite work like that, but concept cars nonetheless remain employer-sanctioned flights of fancy. A way for their best and brightest to toy with new ideas, take design in a whole new direction and gauge public reaction for up-and-coming projects (without exposing the company to financial risk).

Some cars, like the Le Sabre, break through into the mainstream and influence car-design for decades. Others simply grace a single show stand before being mothballed, leaving a legacy of badass photo ops and gawking punters. Yet others become the Batmobile. Whatever their fate, there’s no denying that concept cars are brilliant. Thanks to George from car rental company Sixt, for sending us his list. Please let us know your favourite concept and prototype car designs in the comments below. Below we’ve compiled 20 of our favorites, ranging from the decidedly futuristic to the decidedly oddball:

Buick Y-Job:

Le Sabre:

Cadillac Cyclone:

GM Firebird III:

Ferrari Modulo:

Phantom Corsair:

Pontiac Club de Mer:

Rolls Royce Silver Ghost:

Alfa Romeo BAT5:

Holden Efijy:

Chevrolet Mako Shark:

54 Bonneville:

56 Buick Centurion:

Pontiac Banshee:

63 Corvair Super Spyder:

54 Pontiac Parisianne:

1970 Lancia Stratos:

There you have it: our personal top 20. Did we miss something out? Have you identified a gaping car-shaped hole where your favourite concept should be? Are you right now working yourself up into a state of bucolic rage at our ridiculous oversight? Head down to the comments and let us know.