VATS

The Vault-Tec Assisted Targeting System, or V.A.T.S., is a queuing system for Fallout 3, inspired partly by the ability to shoot specific body parts in the turn-based combat system of Fallout and Fallout 2.

While using V.A.T.S., the otherwise real-time combat is paused. Various actions cost action points, and both the player and enemies can target specific body areas for attacks, inflicting specific injuries.

When using V.A.T.S. against a humanoid enemy, there are generally seven different areas that are targetable; the head, torso, left arm, right arm, currently held weapon, left leg, and right leg. However, there may be other points available when specifically facing off non-humanoid creatures (e.g. Bloatfly wings, Ant's antenna).

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, and combat skill. A higher percentage does not equate to more damage done; for example, an 80% hit to the head/sensors will likely do more damage than a 95% hit to an armored torso.

There is a 15% boost in the chance for a critical hit in VATS.

Unlike previous Fallout games, it is not possible to target the eyes or groin nor target any individual body parts in melee and unarmed combat, however there is a seemingly random chance to decapitate and slice off the limbs of the enemy even though you cannot aim for specific parts.

Effects
Although body part damage can be achieved through manual aiming, VATS allows more effective targeting of particular body parts. The effects of crippling specific body parts is listed below.
 * Crippling the head will reduce overall accuracy and perception of the target. If inflicted upon the player, the screen will intermittently get fuzzy and a ring will be heard through the speakers.
 * Crippling the torso will result in the target flinching far more often from shots than normal.
 * Crippling an arm will result in any weapon reliant on that arm for holding to be dropped, and will also drastically reduce accuracy. The weapon itself is not destroyed, and they will likely just pick it back up again.
 * Crippling a leg will result in impaired mobility. Creatures who rely on leaping attacks (i.e. deathclaws) will no longer be able to use them.
 * Crippling the held weapon will ruin it and make it unusable, and will fly out of the target's hand. If it is an explosive ordinance (like a frag grenade), it will explode, dealing its damage to the target holding it (and any others nearby).
 * Some enemies have alternate targets: Robots, ants, and others have special targetable parts that when crippled will push them into a frenzied state, where they no longer discern between friend and foe and attack anything.

Crippling any body part will result in the target momentarily pausing to clutch the now crippled body part. Specific body parts cannot be targeted when using thrown explosives or melee/unarmed weapons in VATS.

Glitches

 * Sometimes, when the player opens VATS and the targeted enemy walks behind a corner, you wont be able to move until your enemy is dead. What it comes down to is that your followers need to kill the enemy for VATS to close, which might take a LONG time since everything is in slow motion. In some known occurrences(xbox360), this resulted in the death of Dogmeat and the other follower that was accompanying the PC, which in turn allowed the target to live, and forcing the player to reload a previous game due to not being able to close VATS.


 * Update: On the Xbox 360 version, it is not possible to recover from this glitch by holding down the Xbox menu button until the standard VATS target selection re-initiates


 * Occasionaly V.A.T.S. will let players see through walls or rocks.


 * When playing in first person mode, and lining up a shot which is only a few degrees above or below an obstruction, even though you appear to have a clear shot, in V.A.T.S mode, your shots will sometimes hit the obstruction every time. Apparently there is sometimes a slight position difference between first person and V.A.T.S.


 * Sometimes opening vats can cause the whole game to freeze, only confirmed on xbox 360.

V.A.T.S.