Bacalov Instigator Combat Shotgun

The Bacalov Instigator Combat Shotgun (Ithaca 37) sawed-off shotgun in the game. It fires both 12 Gauge and explosive shells. It reloads quite fast and powerful enough to one shot most foes with a single well-round hit. Explosive shells can deal some splash damage around and sweep clear a few foes standing close if you have means of standing at the high ground.

No One Lives Forever 2
Being a loud weapon, shotgun is not a weapon you'd like to use constantly if you don't want alarms blaring all over the place. However it's the reliable close quarter firepower that you depend on when you need to dispatch a large group of enemies after alarms go off, trying to sweep thugs in a bossfight or fighting a Super Soldier. Shooting hauls of pellets once per shot, taking cover or hiding to lure enemies on yourself becomes important.

While 12-gauge buckshot is common standard ammunition and have power to one shot most low ranked enemy from point blank, 12-gauge explosive shells that sweep larger crowds won't make an appearance until Mission 8. As it doesn't accept any competition on terms of damage it lacks in accuracy and effective range, also its ammunition rarity and limited stock becomes a problem. Weapon and Carry abilities make it a threatening presence in combat to stock loads of ammo even though shells are rare to come across.

Contract J.A.C.K.
Unlike NOLF2, shotgun will be a staple for your arsenal when you found yourself pitted against an army of gang members and soldiers. Shotgun is better used when you know foes will flood the area through a narrow gate and aim for very center of them to maximize damage output.

Again, 12-gauge buckshot is common and 12-gauge explosive shells generally show up in limited secret areas that are spread along the chapters. It's quite possible to run dry if you're not conserving ammo as Jack can't stock much ammo, nor have the ability to do so like Archer had.

In game description
While not standard issue for spies, a combat shotgun can be useful in certain situations. Accommodates shells and various type of slugs.

Trivia

 * This gun features no reload animation, as it's simply taken off screen and taken back up after 3 shells have been loaded. Regardless of how many rounds have been fired, Archer/Jack will always load 3 shells into the chamber before pumping the handle.
 * This animation is also used when switching between Buckshot and HE Shells. 3 shells are always loaded even if the players have less than 3 shells in their inventory.

External link
Ithaca 37 on Wikipedia