Vampire: the Requiem's stun grenades have 5B damage. But does it damage only mortals, or vampires too? Stun grenades do damage by loud explosion, so there is a chance that vampires might not be affected. If they are, what happens to a vampire with his Auspex activated?
The damage of a stun grenade — or any weapon — affects vampires normally unless there's a specific exception (e.g. firearms do bashing in nWoD 1.0 and all weapons do bashing in nWoD 2.0).
A vampire with Auspex active would likely have a chance to be stunned just as if startled by a bright flash or another loud noise. If the Auspex writeup doesn't provide rules for that, I'd suggest a Composure + Stamina roll penalized by the damage of the grenade to avoid losing their next action (or, in 2.0, gaining the Stunned tilt).