http://www.amazon.com/Allary-Combi-C.../dp/B00555I79G
Check out this one. I am on my third or fourth one in approximately 30 year period. They stay sharp a long time. It has a small point I slip under the stitches and cut every half inch or so. I have heard the eyebrow trimmers work good. I am not sure I am calling them the right thing. I grew up using a single edge razor blade to rip stitches out with. They work great but you have to be careful to not cut your fabric.