[mirv]

Typically amperage does all the damage to a person, depending if their skin is dirty or not, etc etc (a persons electrical resistance changes dramatically if they have dirty hands, if they sweat, etc). Of course, current is dependent upon the voltage applied across the skin, and the amount of resistance. Puncturing the skin (do tasers actually do this? I've not seen them in action or anything) lessens the resistance heaps, so for the same voltage you'll get an increase current.
About 0.1A can cause death, 0.01A pain, burn, etc, 0.001A a tingling sensation, person depending of course.

And yes, I'm now waiting for the geek alert jokes to begin....I studied this as part of external metal contacts on a hand sign recognition glove.