Wolfenstein: Enemy Territory is a World War 2 first person shooter. There are 5 classes: medic, engineer, soldier, covert ops, and field ops. Each class has their own style, abilities, and weapons. Maps range from deserts to snowy railways. Many of the maps are objective based, for example you may escort a tank through enemy territory. There is also a character upgrade system where you gain enhanced abilities from experience you earn.You gain experience in different ways, depending on class; Medics get xp for reviving people, but everyone gets xp from getting kills with small arms. Your experience may be reset at different times (after a campaign, after you disconnect etc.) depending on the server.
This game is 100% free.