Some of you, I know have come across this problem. If you have been working on these cars for very long, you will eventually break off a screw. (Of course, it is always below the surface and at an angle.) I recently broke off an oil pan screw and have had a bear of a time extracting it.
So, what kind of extractor have you had the best success with? I'm not talking about M10 and M12 bolts, I"m talking about those little M4, M5 and M6 screws. I've done some searching online and there is a vast assundry of "promises" out there, when it comes to this. (Interesting that there are several companies have these for the dental market but ridiculously expensive.)
I know there has to be someone else, besides me, that has a poorly calibrated torque wrench and has snapped a screw.