The Hand of Light was a form of weapon discovered and used by Daniel Jackson during the period that Anubis, allied with the Haaken, attempted to find an artifact of great power. When equipped, it caused a Humans hand to become transparent and reveal the bones within. When it was fired it released a vortex of energy which, when fully powered, sucked beings into oblivion. While a powerful weapon, it became less powerful the more it was fired and had to be charged before it would work at full capacity again. (SG1: "The Alliance")
Behind the scenes
As the Hand of Light only originates in the unreleased computer game, Stargate SG-1: The Alliance, it is unclear as to what their status is in Stargate canon. As the game was originally meant to be canon, it's entirely possible that the weapon is also but, as it was cancelled, there is also the possibility that it is in fact non-canon.