Medal of Honor: allied assault! It was an awesome game and great multiplayer! However after a tiff with EA half the team left and formed.... yes you guessed it... Call Of Duty! In fact I swear the first Call of Duty used many of Medal of Honor: Allied Assault's resources.... many people also claim COD's Stalingrad scene was the origional brutal scene in video games, but it was nothing compared to Omaha beach in the former! Actually many of Allied Assault's maps, especially the multiplayer ones, drew their main influence from Saving Private Ryan....
After that Command and Conquer 3... great game vastly over shadowed by Starcraft II for no other reason than Starcrafts hype, I actually think C&C 3 plays much better!