Find the M-79 grenade launcher on the second to last level (New York Sewers) to unlock the following seven multi-player characters: Ninja Gabe, Scuba Lian, Unit 1 (armored trooper from the Bio-Lab Escape level), Dr. Elsa Weissinger, Uri Gregorov, Lawrence Mujari, and SWAT officer (helped in the New York Slums level). The M-79 is near the end of the level (in the parking garage). Near the top of the stairs is an open doorway into the parking garage, where a black van is driving past. Instead of exiting the stairwell at that location, keep climbing up the stairs. There will be five Agency operatives scattered on the landings above armed with silenced HK-5s, grenades, and M-79s. Use the M-79 to clear them out. The M-79 is on the top landing.