Invisible man

Complete the 'Frontline' level without killing anyone - a pure stealth/pacifist run through the war zone between Red and Fascist lines. Sneak past everyone: stay low, stick to cover and shadow, and don't fire on a soul (knocking enemies out with non-lethal stealth is fine, killing is not). The opposite of Hedge-hopper, so you'll want a separate run for each. Save often and reload if you slip up.