...whatever one's imagination allows.

Needed a reliable, strong clip and settled on the clothes pin spring. Strong, cheap, easy to design around...
Actually these must be the cheapest clothes pins in the world and so are their springs. Next time I'll spend more and get better quality springs.

I've had one clipped wide open for a few days and there's no warp or bending so ABS seems ok here. Jaws are sharp and won't easily let go. Could be longer and wider if desired. The body shape is dictated by the spring... not much room to get creative there.

Metric versions are included.
All I did was scale the STLs up in Blender from my usual units to however many "millimeters" were the equivalent.
Afinia software sees no difference between them. If your print software has trouble properly sizing these files your feedback would be appreciated.

Printing 2 wide halves takes 30 minutes, 15g ABS using Afinia default settings.. 0.30mm Z, medium speed and fill, with a raft.

Other variations on clothespin clips:
http://www.thingiverse.com/thing:680130
http://www.thingiverse.com/thing:677020