Alien Swarm -
https://store.steampowered.com/app/630/Alien_Swarm/Alien Swarm: Reactive Drop -
https://store.steampowered.com/app/563560/Alien_Swarm_Reactive_Drop/[Officer]
The Officer uses Officer Skills, and applies damage and defense buffs to nearby squadmates. They are harder to kill than some marines.[Special Weapons]
The Special Weapons marine uses Special Weapons Skills and has a higher overall damage capability. They are good at mowing down swarms.[Medic]
The Medic uses Medic Skills, and has access to a variety of mass or singular healing tools to heal friendly marines and counter infestations from parasites.[Tech]
The Technical Specialist uses Tech Skills, and can hack security consoles. They are necessary for the completion of most missions.