I found a few bike videos on YouTube that stretch the imagination:
Here is water filter on wheels, a really good idea:
Check out this home made kid’s tandem.
Here is something I had not seen before, a back to back tandem:
Ok, how about a back to back recumbent tandem?
Here’s a new brand, look ma, no hands!
How about a propellor driven trike?
Finally, the world’s fastest human powered bike, a recumbent of course: