Sniper, Engineer, and Scout.
Pretty obvious, really. They can easily defend a building by Engi putting a sentry on the ground floor near the stairs, put a dispenser on the top floor to give Sniper ammo, and have Scout go out to get food and water.
Pretty obvious, really. They can easily defend a building by Engi putting a sentry on the ground floor near the stairs, put a dispenser on the top floor to give Sniper ammo, and have Scout go out to get food and water.