Fallout: New Vegas combat

Fallout: New Vegas has a combat system that is very similar to its predecessor, Fallout 3.

V.A.T.S.
The Vault-Tec Assisted Targeting System returns to Fallout: New Vegas allowing the player to freeze combat and specifically target six different limbs at the cost of action points. Largely unchanged from Fallout 3, although certain changes were made to lessen V.A.T.S over-reliance while also reward players with special attacks for their advancement in Unarmed and Melee Weapons skill.

Changes

 * After reaching a Melee Weapons skill of 50, every melee weapon can execute a special attack with varying effects.
 * At Unarmed level 50, unarmed weapons gain Uppercut and Stomp special attacks, and the Cross special attack at skill level 75. Each have their own special properties but all attacks have an AP cost of 20 regardless of weapon used.
 * Base melee/unarmed damage (except thrown melee weapons) dealt by the weapon is automatically doubled.
 * In V.A.T.S. taken damage increased from 10% to 75% making death in V.A.T.S. an always present threat.
 * V.A.T.S. critical chance bonus decreased from 15% to 5%.
 * V.A.T.S. no longer inflicts additional weapon's durability damage on use.
 * Enemy slow down modified. All enemies move slower in V.A.T.S., but those not actively targeted are not as dramatically slowed.

Aim down sights
A new feature in Fallout: New Vegas allows the player to aim down the sights of their firearm, as opposed to in Fallout 3 where the "aim down sights" was simply a zoom in feature to the side of the weapon. Additionally, weapon sway and a variety of variables that effect weapon spread have been added to give projectile weapons a more realistic feel.

Combat damage

 * DAM = Derived in-game statistic representing the power of a weapon. Not used in calculations
 * DMG = Unmodified weapon base damage. DAM is equal to DMG with a weapon at full repair, 100 weapon skill and no damage modifying perks
 * CRITDMG = Unmodified bonus damage added for critical strike on target
 * SA = Sneak Attack modifier adds +100% total damage
 * BC = Better Criticals modifier adds +50% critical damage
 * HS = Headshot modifier adds +100% total damage
 * DT = Damage Threshold of target
 * AM = Ammunition type multiplier
 * DM = Difficulty multiplier. One on normal difficulty, 0.5 on very hard.
 * PERK MULTIPLIERS = Other damage multipliers from perks such as Lord of Death, Bloody Mess and Living Anatomy

The damage formula is calculated as follows:
 * Damage inflicted = (DMG + (CRITDMG x BC)- DT) x SA x HS x AM x DM x Perk multipliers

The main thing to note is that target's damage threshold is subtracted directly from base weapon damage before any multiplicative modifiers are applied.