The M9 is a reliable semi-automatic pistol with a 10-round magazine and suppressor support. It is a sensible early sidearm, also appears in the Pagan: Control DLC, and has Pistola Sportiva as its unique version.
It is a steady early pistol for quiet headshots once you add a suppressor. The 10-round magazine gives you a bit more room than the PM or 1911. It falls behind once you find a stronger sidearm.
It takes standard, armor-piercing, soft-target, poison, blast and incendiary rounds. The muzzle socket fits suppressors and the optic socket takes reflex and red dot sights.
The 1911 fires faster and is more desirable overall. The 6P9 comes suppressed already. The M9's advantage is its larger magazine.
.44 Magnum
The .44 Magnum is a six-shot revolver-style pistol that hits hard for a sidearm. Its two unique versions, Magnum, P.D. and The Big Dog, give you a quick-draw backup with real stopping power at short to mid range.
1911
The 1911 is a rare semi-automatic pistol in Far Cry 6, and one of the best all-round sidearms you can find. You unlock it through the And The Beat Goes On... treasure hunt, and it is Vaas's starting weapon in the Vaas: Insanity DLC.
57 USG
The 57 USG, sold as The Diplomat, is a high-capacity pistol from the Far Cry 6 online store. Its 20-round magazine and full set of mod sockets make it a flexible sidearm if you own it.
6P13 Auto
The 6P13 Auto is a fully automatic machine pistol with a 40-round drum. It sprays fast at close range, and its unique versions come from Los Bandidos operations and two insurgencies.