--> EDIT 2015-01-15: I added a doublesided version with both directions in one tool, righty tighty and lefty loosey. :-) <--
--> I saw a ton of these already but since my version is a little bit different and I put some work in it I decided to upload them anyway.
The NASA Space ratchet wrench (http://nasa3d.arc.nasa.gov/detail/wrench-mis) - first e-mailed and printed tool in space- only tightens. So I mirrored it and created the Righty Tighty Lefty Loosey set :-)
3DWP delivers service in 3D printing/scanning/designing. We can be of great value because of our extensive experience in Additive Manufacturing.
3D Print Service 3DWP website: https://www.3dwp.nl
Website about free 3D printer software: http://www.gratis3dprintersoftware.nl
3DWP on Shapeways: https://www.shapeways.com/shops/3dwp