The best I have ever used were a very small razor one a LAer gave me. she buys them in bulk but I cannot find them anywhere. I also have Clover ones which I like especially the ones that are rounded slightly and I have the one posted above that have the razor on the end which you can replace.
I have also used small manicure scissors. so I guess it is whatever I grab first..lol My motto whatever it takes to get er done!