To dull the senses, as with a heavy blow, a shock, or fatigue
To render helpless, as by emotion
To render unconscious
If you're looking to stun, look no further than the Cellini line.
There's also a ring called the Stun Ring that has pepper spray in it.
Stun guns will zap a would be attacker with a high-voltage, low-amp electrical volt that will disable him temporarily but not cause permanent damage.
Remember that the wounds from a gun cannot be reversed, such as with a stun gun or pepper spray.
Tilt Skull: Enhancing the stun resistance of enemies, this skull is in Cortana.