The primary fire shoots several pellets. The pellets are fired in a spread, which becomes larger the further away the target is from the player. There is a noticeable delay between shots. Each shot uses a medium amount of ammo.
The alternate fire mode shoots a smoke bomb. When the smoke bomb hits something, it will explode, releasing a wall of smoke. The smoke will blind anyone that is in the smoke wall. This firing mode uses more ammo than the primary fire does.
The shotgun works best at close or very close range. At these ranges, most, if not all, of the pellets will hit the enemy.
Engaging at medium range with the gun does have noticeable drop in damage compared to shooting at close or very close range because less pellets are hitting the enemy. It is still powerful, but not as powerful as shooting at closer ranges would be.
A Refire rate mod will make the shotgun much more useful. Being able to fire shots faster makes it a lot easier to defeat an enemy, which can mean the difference between living and dying. This mod also make it more better at medium range because it lets the player fire more often in order to compensate for some of the pellets missing.
Modding the shotgun with the Fragmentary round mod makes it quite useful against humans and monsters/transgenics. In Normal difficulty, two shots are all that's needed with a fragmentary round-modded shotgun to defeat normal human opponents.
The smoke grenade alt-fire is useful, but the smoke it spews makes it hard to see stunned enemies. Charging it might be dangerous if some of the enemies have not been affected by the smoke.
Stunning enemies with the smoke grenade can be handy, but the amount of ammo each grenade consumes means that the player should try to limit their use of it to when it's really needed. Otherwise, they might run of out ammo.
Having a ranged weapon, like the Assassin Pistol or the sniper rifle, is a good idea. These weapons let the player engage and quickly kill enemies at ranges that the shotgun would not be very effective at.
The Speed Enhancement aug works well with the shotgun. With the aug on, shotgun users can quickly circle-strafe enemies, making it hard for enemies to shoot the player while the player can consistently land shots on the enemy. The aug can also be used for running up to an enemy, shooting them at point blank range, then quickly retreating before the enemy can get a shot off.