Based on luchocarreno's Print-in-place ratchet clamp, I gave it my own shot.

This clamp is not print in place! It uses an embedded M3 nut, placed in one of the two arms and is fixed together after the print with an M3x10 screw.

Pause your printer in between layer #18 and layer #19 to put the nut in place.

As usal, the 123D Design file is included. So feel free to give it your own twist.