I've had numerous clients who fought through a taser. These are not guys with particularly great Ego or other stats. They're guys with straight-8s.
A "real world" taser is probably a 3D6 or 4D6 EB, with limited range, a 14- activation (sometimes it gets caught in clothing or just doesn't work for some reason), and whatever other limitations are appropriate. Maybe even a "can't reduce below 1 Stun" custom limitation since people don't seem to lose consciousness. That's enough to put a normal dude on the ground and make him really not want to fight. It also leaves open the possibility that the attacker rolls like crap and people shrug it off.
Movie tasers and other things like that may be different, but at least for the real versions I'd get away from "auto-stunning" and other effects. They just aren't that good.