An innovation of Admiral Daro'Xen, the Arc Pistol is a scaled-down Arc Projector that only requires thermal clips, to solve its power problems. The Arc Pistol uses a nonvisible laser to ionize the air and create a path for a high-ampere electric shock. For a more damaging blast, it can be charged up.
When using the Arc Pistol, individual shots should be used on weaker enemies and charged shots should be used to devastate armor, shields or barriers.
A good way of utilizing its dual fire mode is to shoot a few uncharged rounds at the enemy, and when they stagger/dodge, unleash a charged shot to their head after they finish.
The Arc Pistol, being more readily available, is a fantastic (if slow-firing) substitute for the ultra rare M-77 Paladin: the Arc Pistol does more damage when fully charged, has a more accurate reticule that doesn't expand, and has a larger base clip size (6 fully charged shots for the Arc Pistol compared to 3 for the Paladin). In addition, its rare status means that it is significantly easier to acquire the relatively lighter Arc Pistol X than the Paladin X.
Uncharged shots are comparable to the M-3 Predator in damage.
Technically, the Arc Pistol has the lowest rate of fire in the game if the player only fires charged shots.
Fully-charged shots consume 3 ammo while firing three shots at triple damage, resulting in 9 times the damage of an uncharged shot. With the base headshot multiplier of 2.5x, a single charged headshot can do 22.5x damage! Combined with Stasis, Warp, and Warp Rounds, consistent marksmen can wreak havoc on opponents both large and small.
The Arc Pistol suffers in the same way as the Graal Spike Thrower and other charge-for-max-damage weapons on higher difficulties; in order to do maximum damage, you must expose yourself from cover for a fair while. In these situations it is better to carry either the Carnifex or the Paladin, neither of which have a charge time.
However, it also benefits Infiltrators in the same way as other, chargeable weapons, without the huge power recharge increase that both the Geth Plasma Shotgun and the Kishock Harpoon Gun have - if charged up before going into cloak, an Infiltrator can fire off the charged shot without breaking cloak.
The Arc Pistol benefits a lot from the addition of the Piercing Mod, as well as the High Caliber Barrel mod since these maximize the damage it can do to armored targets.
Its already large clip size and ammo pool mean that it benefits less from a Magazine Upgrade mod than other pistols, since it has a slow rate of fire (for fully charged shots) and can be easily reload-cancelled anyway.
Combining the High Caliber Barrel with the power magnifier makes the Arc Pistol a very versatile weapon, as it improves overall performance of those solely or mostly reliant on their powers. The extra damage can help headshot targets at a distance, or where powers may not reach or may be blocked, and allows users to maintain lethality when powers are cooling down. Armor piercing ammo can help mitigate the lack of penetration and even level 1 ammunition of said type can still do just as much armor damage as the piercing mod, although piercing abilities are significantly reduced. Since the Arc Pistol can be spammed in close quarters, or used like a sniper at medium and long ranges (without penalties) it can be used as a sole weapon or as a backup weapon due to its fairly low weight.