This looks like a grenade with an ARB casing and a clawed demonic hand for a pin. To charge it up, plug it into an AI/O port and wear it while you are struck for damage. You then unplug it and keep it handy until you want to throw it.
Record the Pain Charge of the Agony Grenade. It is equal to the greatest number of Wound points you took from a single source while wearing the Agony Grenade, divided by 3. Multiple attacks do not accumulate a charge; it only charges once.
When it hits the ground, it emits arcane energy over an area. Make a Powers check against the Pain Charge; the Outcome is the radius of the effect in meters. Compare your Action Result against the Dodge of characters in that area; those that are hit suffer Impairment penalties. Impairment is equal to the Pain Charge. They do not suffer any actual injuries from this effect; the arcane energy is stimulating the pain centers in their brains.
Only living beings are affected by agony grenades. The effect lasts for a number of shots equal to the Outcome of the Powers check versus the Pain Charge. The effect clings to the characters, not the area; the grenade immediately grows inert.
There is a mystic link between the character charging the agony grenade and the grenade itself: if anyone else attempts to throw an agony grenade, it is a dud.
Agony grenades retain their charge until the end of the session: at the start of the next session, any charged grenades have lost their charge completely.
If you take this schtick, you have an essentially unlimited supply of grenades, but can keep only one charged for each Agony Grenade schtick you've taken. Of course, you can always be separated from your bag full of the things if you get captured or fall out of a plane or something like that.
The Agony Grenade is not a gun, and cannot use gun schticks. It cannot be thrown with Martial Arts or combined with Fu schticks. It only works with Powers.