More sidearms utilized by the United Sovereignty of Nations during the time of Project A:
1: M-12 Tesla Magnum: The USN prefers a fair amount of variety in it's ground troop weapons, so although the D-14 Jackhammer may be a great heavy duty sidearm, it has a counterpart nonetheless. Arguably even more powerful than the Jackhammer, the M-12 Tesla is essentially a full functioning railgun magnum; instead of firing a chemical assisted projectile, the weapon is fully magnetic accelerated. Mobility is sacrificed for power however: it is bulky, heavy, and has recoil roughly 40% more than that of the D-14 Jackhammer. The weapon magnetically propels 6.5mm by 10mm caseless projectiles at a muzzle velocity of 1000 m/s, and commonly utilizes a 9 round mag. The battery at the back, which also serves as a counterweight, holds enough charge for 126 shots.
2: M-4 Inferno Pistol: Though not often utilized, flamethrowers have their uses as weapons of shock, awe, and suppression. The most compact form of flamethrower utilized by the USN military is small enough to be held in one's hand, and can be a great weapon for close quarters situations. The weapon's canister has enough fuel for a 20 second continuous stream of fire, with a decent effective range of around 29.5 meters; the primarily azure flame burns at around 2200 K. Not much more can be said about this sidearm; it's a mini freakin' flamethrower.
3: XE-Laser Pistol: The name speaks for itself. This twin barreled weapon fires highly focused, high energy beams of crimson red light. Because of the nature of the weapon, it has great range, essentially no recoil, and is much quieter than projectile firing weapons. The sound it does produce is something of a sharp whine or pop, and that's from the heat of the lasers expanding the air around the barrels with each shot. The only possible downside it that the weapon's flash can damage the user’s eyes if they are unprotected. The XE-Laser Pistol has a full semi-auto rate of fire and a 25 shot rechargeable battery, along with a built in flashlight.
4: 12-G Pepperbox: A somewhat uncommon sidearm, the 16-G Pepperbox is an ultra compact shotgun weapon. As one could imagine, the weapon is almost exclusively used for close quarters combat, such as in buildings, trenches, or dense forests. Particularly, a fair number of Navy personnel prefer this weapon as their sidearm, considering that the tight halls and passageways of a ship are perfect for the weapon's short range. Despite being a semi-auto shotgun, it has decent firepower and stability. The Pepperbox primarily utilizes a 5 round magazine carrying a similar equivalent to 12-gauge shells.
(Picture may be subject to change, if I can get a better photo of the drawing)