Aside from the Ultor weapons, the Mercenaries bring their own weapons for their liking.
The Precision Rifle is the "sidearm" and primary weapon for most of the Mercenaries especially Grunts. It fires 5.65mm explosive ammunition and comes with an unnamed attached scope. It fires in semi-automatic bursts.
The Rail Driver is a directed-energy weapon that is capable of shooting rail slugs through environment. It instantly kills nearly anything. The Rail Driver comes with an X-Ray vision scope. The Mercenary Commandos primarily use this weapon.
The weapon where Mercs use to go from dreadful to painful. The HMG fires 7.62mm rounds at great speed. It is wielded by Mercenary Heavies.
The Fusion Rocket Launcher fires a shell which makes a large explosion, killing anyone in its radius.