'Free to play' WW2 combined arms FPSMMO. Recently released on Steam but originally released in 2001. One month free trial for Steam users and then subscription or you can just play for free with a limited amount of equipment. Huge variety of roles from all kinds of infantry to flying bombers and fighter planes, tanks, trucks, anti-air and anti-tank guns or boats from small patrol boats to destroyers.
Play as a German on axis or British, French or American on allies. Campaigns are centered around capturing buildings as infantry with various functions such as infantry spawn or vehicle spawn and in turn taking entire towns and cities of varying sizes. The map is the largest ever made for a game at 'over 350,000 km2(135,136 sq mi), with most play occurring in a 52,000 km2 (20,077 sq mi) central area in which most capturable cities, airfields and ports have been placed'. This area is essentially a half scale map of much of Western Europe. Campaigns are led by voluntary high command players who choose what supply is going to which town and where attacks will take place. Battles for towns and cities can go on for weeks, campaigns can go on for months.
Not a game for everyone. There is a steep learning curve, the graphics are functional (to put it politely) and there is a huge amount to learn. When the game is really great, as it has been since release on Steam beause the population is now excellent, the battles are fantastic. A few nights ago a battle for a town lasted two hours and involved at least 150 people on each side including tank columns rolling in, paratroopers being dropped overhead as a dogfight with scores of planes was happening overhead and many related battles of all kinds for miles around the objective.
I could go on, this game is really deep. I doubt most people will really enjoy this game but for sheer ambition and uniqueness I highly recommend it to any FPS and/or WW2 fan.