A simple desktop universal joint.

Print (I made it all of ABS, .2mm layers):
4 - Forks
2 - Blocks
1 - Intermediate Shaft
1 - Crank
2 - Long Pivot Pins
4 - Short Pivot Pins
1 - Crank Shaft
1 - Drive Shaft
1 - Frame

You'll get the best results if you glue everything together, although the parts are somewhat tight-fitting.

Start by gluing the intermediate shaft in the bottom hole on two of the forks. Make sure the faces of the forks are parallel to each other.

Glue the Drive Shaft to the bottom hole of the third Fork.

Glue the crank on the end of the Crank Shaft. Slide the Crank Shaft Assembly thru one of the holes in the frame, and then glue on the forth Fork.

Finish the assembly by using the Long and Short Pivot Pins to hold the Blocks in the Forks.

Spin and enjoy!!