I have one (and a stun gun as well)...
I've tried the cattle prod on myself a few times - I don't find it particularly painful (though I'm only using it on my calf) - more just a sharp zap. It's more a surprise sort of shock if you know what I mean.
I use it quite a bit in session - it's apparently a *lot* more painful on genitals than it is on legs - snicker... if you use it a lot on the cock it will produce an oedema that takes a couple of hours to come up and couple of days to go down. Two or three zaps are less likely to do this.
I'm not sure exactly what sort it is - it has a medium length handle "prod" part rather than being a small hand-held unit... I thought it was more intimidating that way
It was a gift from a certain sub - hehe.
I can look up the paperwork if you like and give you more info.