Red Orchestra Ostfront 41-45
 

This game is about World War II, playing as Germans & Russians on the Eastern Front. It may be old but many still play. There is an awesome MOD, called Darkest Hour, changing the maps and units to a whole new level.

Get it from Steam.
http://store.steampowered.com/app/1200/

German, British, and Americans on the Western Front, new weapons, vehicles, and plenty of maps for both sides. Not including the uniforms, great in detal!
http://www.darkesthourgame.com/