Surprised there are not more as all people seem to be doing is putting something like "unusual cars" into Google
Yes agree, i always like to go from one starting point and see where it leads me to by linking and personal associations and use different search terms to discover things i couldn't think of myself.
Anyway, here's an interesting vehicle by Pininfarina, the 1960 X-concept which has 2 wheels in the middle ( front/rear ) and 2 wheels on the side.
There are more cars with this sort of experimental wheel lay-out but this one is the most famous.
And i'm not sure i want to introduce a new category of cars to this thread because of its possible implications, but they couldn't be much worse than some suggestions ( kitsch-cars ) on this thread anyway.
So here are some kitcars, a different unlikely category for inclusion in GT although technically still cars, and although the majority of kitcars will rightfully raise some eyebrows, some are interesting and even "classics" in their own context.
So no replicas of existing cars but originally designed vehicles which use humdrum cars as basis.
Here's the Nova kitcar with fully functioning canopy, this one is powered by a Boxer-4 Alfa Romeo engine.
And here's the Phoenix Camper Van based on a Volkswagen.