Digging up a couple of things I did this year, had my own personal 48h game jams except they weren't really, I just give myself a limit of 48 hours total whenever I feel like I need to sketch out an idea.
Prototype 1: Glider
Prototype 2: Super Rally Sprint
Here's a demo of the car thing
http://crudepixel.com/2014/10/car-thing/