Reputation

Reputation is the opinion of the public toward a person or a group of people.

Fallout
Reputation in Fallout can be considered the equivalent of Karma from Fallout 2. Besides global reputation, the character can be endowed with various reputation perks.

Fallout 2
Reputation in Fallout 2 is a way to measure general feeling for your character in each of the towns you visit. Reputation can be modified by doing good or bad deeds, like completing quests or killing townsfolk.

Fallout Tactics
Reputation in Fallout Tactics is the reflection of what people think of player's character, based on his/her action. Characters start with the reputation of a Warrior, and move up or down from there.

Fallout: New Vegas
In Fallout: New Vegas, your reputation among various factions will be tracked, and will even give you access to new areas in the game.

There are many different factions in the Wasteland, and you can develop a distinct relationship with each one. As you perform actions that benefit a group, you will gain Fame. If you perform actions that harm a group, you will gain Infamy. Your reputation with any given group is a measure of the combined total of Fame and Infamy that you have earned. The benefits and drawbacks of any given reputation depend of the group itself. You may receive discounts with merchants, provoke attacks from hired thugs, or simply be treated differently.

Any faction member can be killed with no loss of reputation, though only if the player remains hidden or in caution for the kill without it progressing to danger.