The Goa'uld hand device is a type of exotic personal weapon, resembling a jewel attached to the user's hand.
Hand devices posses several functions. Used as a weapon, they generate shockwaves capable of knocking down an adult human. As a torture device, they can be held close to a prisoner's head, inflicting excruciating pain without leaving physical injuries; this mode can also be used to transfer information from one individual to another.
Hand devices can only be used by present of former Goa'uld hosts. These are not weapons of war so much as defensive side-arms.