This design is a prototype of a purely printed bottle opener design, which means you don't need to add a coin or other metal parts for stability. It's designed to require minimum force and has maximum stability at the critical point (where the cap is lifted).
My printed prototype withstood about 15 bottles of my favorite German beer until it broke. So the current version can only be seen as an "emergency" bottle opener but nothing which lasts long.
An optimization to this as well as an alternative design (also without metal) is under development.
Please read print instructions for good results!
The model is designed in Blender with bezier spline curves, the Blender source file is also available for download.
Print this with some extra shells, solid top and bottom layers as well as with not too low infill to reach a good stability. I used 0.3mm layer height, 3 shells and 5 full layers at top and bottom as well as 30% infill. I filed the surface after printing, which removes ~1 layer.
I used ABS, but PLA might be even better (but I don't have any experience with PLA).
You might want to file a bit off from the (in the picture) left part if you can't open a bottle with it. It's designed to perfectly fit the bottle cap, but if it is too tight it might not pass the glass once the cap is lifted a bit (see second picture).