VATS (Fallout 3)

V.A.T.S. or the Vault-Tec Assisted Targeting System is a statistic-based combat system

Gameplay
While using V.A.T.S., the otherwise real-time combat is paused. Various actions cost Action Points, and the user can target specific body areas for attacks, inflicting specific injuries.When using V.A.T.S. against a human, super mutant, or ghoul, seven different areas can be targeted: the head, torso, left arm, right arm, currently held weapon, left leg, and right leg. Robots and creatures have additional targets such as antennae.

When targeting a part, the screen displays a percentage of how likely the attack will hit the targeted area based on distance from the target, visibility of the targeted body part, and combat skill. The percentage of a hit cannot be any higher than 95%. The readout also displays the overall condition of the body parts on the target. The bar will be empty when the limb has been crippled.

V.A.T.S. also displays a health meter indicating the target's overall health, as well as an indicator showing the amount of damage a V.A.T.S. attack round using the character's current weapon will inflict. There is a 15% boost in the chance for a critical hit in V.A.T.S. mode, but weapons degrade at 4 times the regular rate.

Effects

 * Crippling any body part will result in the target momentarily pausing to clutch the crippled body part or reel from the injury. When using explosive and melee weapons specific body parts cannot be targeted while in V.A.T.S. as the enemy is targeted as a whole.
 * Crippling the head will reduce overall accuracy and Perception (-4) of the target. If inflicted upon the player character, the screen will intermittently blur and a ringing audio effect occurs.
 * Weapon accuracy is reduced in V.A.T.S. by a crippled arm, but still allows using weapons. A crippled right arm also reduces base melee damage done by 10% if wielding a one-handed weapon. If wielding a two-handed weapon (or unarmed), one crippled arm reduces base damage done by 5%, two crippled arms reduce base damage done by 10%.
 * Grenades can be targeted by V.A.T.S. while in the air after being thrown. If successfully hit on the fly, they will explode prematurely.

Bugs

 * On rare occasions, the black-and-white effect of V.A.T.S. will carry over to the normal game, rendering everything except the HUD in a permanent grayscale filter.
 * Firing weapons that require two shells, such as the double-barrel shotgun, while possessing only one can lead to a bug in which the character does not actually fire a shot in V.A.T.S. It will just result in a drawn-out cinematic view of the player aiming at their target.