A smoke grenade (2370)
A smoke grenade was a non-lethal bomb that gave off thick smoke when it exploded. They were usually used to provide cover in the form of a smoke-screen.
In 2370, an unnamed Starfleet officer threw a smoke grenade to provide cover for Chief O'Brien and Li Nalas after they were pinned down in the promenade security office, during General Krim's take-over of Deep Space 9. (DS9: "The Siege")