My local soda bottler must have set the torque pretty high on their bottle capper because I was tearing up my hands opening the bottles recently. Rather than hit the "As Seen On TV" asile to look for a solution, I just designed up soda bottle cap gripper with OpenSCAD and printed my own. I mainly wanted to see if my MakerBot could make a part detailed enough and strong enough to do the job. Happily it does. The tighter the cap, the stronger this thing grips (probably until something breaks...)
You can play with the parameters to tune the gripper for your particular brand of soda.
12/5/13 - Added a chamfer to the top edge of the gripper/opener.
I printed this gripper with a MakerBot Replicator 2X in ABS with 10% infill and 1 shell. The rest of the setting were at default.