The following weapons were used in the movie Cube Zero:
Heckler & Koch PSG-1 (converted to tranquilizer gun)
Government operatives tasked with retrieving "subjects" to be placed in the Cube utilize the Heckler & Koch PSG-1 rifle. The rifles used have been converted into dart rifles that fire a tranquilizer dart. The conversion consists of an apparatus located beneath the handguard that is connected to a hose that travels into the weapon's magazine well. How this system actually operates is never shown.
One of the soldiers sent to capture Rains and her daughter has an M4 Carbine slung over his back.