Reputation

In video gaming, Reputation is a numerical score, often not shown to the player, which influences how factions of NPCs within the video game react to the player, and may even influence what the player may buy and/or sell to them.

An evolution of the system could be described as the Paragon/Renegade system, used in games such as Mass Effect.

Implementations
One of the most obvious implementations of a reputation system lies in World of Warcraft and it's subsequent expansions.