A stun grenade or flash grenade was a hand-thrown weapon. It was utilized by both Starfleet and MACOs in the 22nd century, as well as the Terran Empire in the 23rd century. Designed with a time-delay setting, stun grenades were capable of incapacitating the enemy without causing permanent physical damage, in much the same way as a phase-pistol set to stun.
When Lieutenant Malcolm Reed was held hostage by the Novans beneath the surface on Terra Nova, Commander Trip Tucker suggested using a stun grenade but Captain Jonathan Archer ruled out this possibility as he didn't want any more casualties. Later, when talking about a possible removal of the Novans from their underground tunnels to save their lives, Sub-commander T'Pol suggested again the use of stun grenades to remove the Novans by force. (ENT: "Terra Nova")
The next year, Captain Jonathan Archer, Commander Tucker, and T'Pol, utilized stun grenades in a raid of a Suliban stealth cruiser, during their attempt to obtain evidence that the Cabal had framed them for the destruction of a colony at Paraagan II. (ENT: "Shockwave")
Shortly into their mission in the Delphic Expanse, Enterprise was raided by Osaarian pirates. During their attempts to subdue the Osaarians, Captain Archer ordered a MACO to utilize a stun grenade to neutralize one of them in the armory, as using their phase weapons in such close proximity to armed photonic torpedoes was too dangerous. The stun grenade proved ineffective, however, as the Osaarian was able to beam away before it went off. Amongst other items stolen by the pirates were two dozen stun grenades. (ENT: "Anomaly (ENT)")
During a Starfleet mutiny in January 2154, a stun grenade was lobbed inside an airlock aboard a crashed Xindi-Insectoid starship by Commander Charles Tucker III. The weapon's detonation rendered two MACO guards unconscious, inside the airlock. (ENT: "Hatchery")
In 2154, stun grenades were used by the Enterprise crew during their raid of an Illyrian starship, designed to forcibly obtain their primary warp coil. (ENT: "Damage")
Later that year, Major Hayes and a team of MACOs used a stun grenade to incapacitate two Xindi-Reptilians during a boarding mission to a Xindi-Reptilian warship aimed at rescuing Ensign Hoshi Sato, who had been kidnapped by the Reptilians. (ENT: "Countdown")
Although the script of "Countdown" referred to this device as a "grenade", the script also stated, "This was clearly not a stun grenade."
In 2155 in the mirror universe, T'Pol used a stun grenade to incapacitate two MACOs who were guarding Captain Forrest, who had been imprisoned by Commander Jonathan Archer, and subsequently break him out of the brig. (ENT: "In a Mirror, Darkly")
Forces loyal to Gabriel Lorca used a flash grenade against Emperor Philippa Georgiou and her forces in an attempted coup, but she performed an emergency beam out to escape. (DIS: "What's Past Is Prologue")
Several prop stun grenades were sold off on the It's A Wrap! sale and auction on eBay. [1](X) [2](X)
Apocrypha[]
Stun grenades were also available as a playable object in the 2013 Star Trek video game.