Fist

Although Fist is not a regular item in-game, lacking physical representation other than the icon in the toolbar, it is a selectable weapon treated as as item in-game.

For all classes other than Monk, Fist is the only weapon that deals non-lethal damage, allowing to make enemy unconscious without killing him, allowing to get away from fights without losing reputation or an alternative way to steal items from containers without alerting guards, as unconscious NPCs don't bring alarm up. However, while allowing to avoid the reputation loss, the enemy will permanently remain hostile toward you, with the only option to temporary alleviate it by charming.

Monk's Fists
For Monks, fists are used as a main way of fighting, unlike the other classes. They lose the way for fighting unarmed, though. During leveling, as they fist become treated as a magic weapon, they are called Fist +1, Fist +2, Fist +3 and Fist +4 respectively in and.