Action point costs for all weapons are reduced by 1 AP. The player cannot make called shots to body parts.
Fallout 2, Fallout Tactics and Van Buren
In subsequent games, the AP costs are reduced by 1 AP for all ranged (conventional and energy weapons), but at the penalty of being unable to aim.
Fallout: New Vegas
This trait reduces accuracy with Energy Weapons and Guns by 20% while increasing the fire rate by 20%. This reduction in accuracy reduces the chance to hit when firing in V.A.T.S. and increases the amount of sway when taking zoomed shots out of V.A.T.S.
Ironically, this trait is best suited to players who like sniping. Sniper rifles have low spreads and the reduced accuracy is negligible, while the increased speed helps compensate low rates of fire. Conversely, automatic weapons, with their high base spread, suffer the most from this trait. Players who prefer to "run and gun" may want to consider Trigger Discipline instead.
This trait works extremely well with other AP reduction perks like Math Wrath.
In early patches, this trait will reduce your maximum accuracy in V.A.T.S. to 76% (as of 1.4.0 PCXbox 360 / 1.7 PlayStation 3 this is no longer the case). This can be rectified by the Gunslinger, Commando, or Sniper perks.
J.E. Sawyer's Fallout RPG
During the charge phase, you can fire a firearm instead of charging (eliminates you from the action phase of that round), but your critical hits with firearms always come in 6 point increments.