The N7 Piranha is an assault shotgun designed for the Reaper war. When the N7 program began training alien resistance forces, the lighter-bodied species wanted a low-recoil weapon with a wide pellet spread for dealing with hordes of husks. The result was the Piranha, which hit a sweet spot in close-range firepower. Its rapid-fire capability tears apart not only husks but most opponents unlucky enough to be in its way.
The N7 Piranha can be devastatingly powerful, especially if the damage or fire rate is bumped up. Its potential is limited to the close range game, however, as the weapon suffers from a very steep damage reduction at longer ranges. Because of this, the Piranha is best suited for close-range classes like krogan, vorcha, or Project Phoenix humans. The recoil on this weapon is very easy to control, requiring little to no correction. The Piranha is fully automatic, and can chew through ammo quickly if the player is not careful.
Unlike other shotguns, when aiming down sights, instead of a circle you will see cross-hairs like that of an assault rifle, heavy pistol, or SMG. The cross-hairs will give the player a spread covering almost the entire screen. A Shotgun Smart Choke and/or firing from cover can remedy this to the point that the spread will be similar to that of an un-modded M-300 Claymore.
Because of the spread of the N7 Piranha, it is not a bad idea to fire without aiming down sights, since the accuracy and recoil of the weapon are very forgiving. The damage done to a target will usually be enough to stun them, giving you the perfect opportunity for a salvo of follow-up shots.
The N7 Piranha I is more powerful than the Katana X with matching mods. A Vanguard armed with this weapon is one of the most deadly forces on the front lines. 2-3 clips on Bronze will kill a Banshee at full stats and 1-2 will kill a Brute. Using a Biotic Charge to stagger an opponent will buy you enough time to empty the clip and run back for a reload before the opponent recovers, if they survive the first clip. Weighing in at 1.5 times the Katana X's weight, it still leaves space for a heavy pistol or SMG when the Piranha runs out of ammo, or for mid- to long-range combat.
A Turian Soldier, using this weapon in addition to the Marksman ability, the shredder and smart choke mods, is very effective at dealing with unarmored and armored targets from afar. The bonus stability and rate of fire given by Marksman grant the player the ability to "snipe" targets from very far, making it an incredibly versatile weapon.
This weapon is very effective when employed with the N7 Destroyer Soldier, due to the increase in clip size, rate of fire, and damage. Since its spread is also tightened by Devastator Mode, the Piranha can easily shred through whole groups of enemies in very short order. It also works very effectively as a boss-killer, capable of very swiftly tearing through shields/barriers, and armor. That being said the only problem will be making sure your ammunition supplies are topped up, as the Destroyer will go through his ammunition supply even more rapidly.
A Geth Hunter Infiltrator is also very effective when using this weapon. Evolve Tactical Cloak to do more damage and evolve Hunter Mode to increase damage, firing rate and accuracy. Use Proximity Mine to stagger opponents and debuff enemies, resulting in an almost unmatched damage per second (DPS). The primary pitfall of this build comes down to the extremely low health of the Geth Infiltrator while in Hunter Mode and the speed at which ammunition is used. When used with proper equipment, Brutes will fall in 1 clip.