Call of Duty 2 Codes -

Level select
Hold + then quickly press , , , , , at the mission selection screen.

Achievements
Play a Single-Player campaign mode and accomplish a certain task to unlock these achievements for Gamerscore points:

Completed Training - 50 points Complete the Basic Training Level
Veteran of Crossing the Rhine - 60 points Complete Crossing the Rhine levels on Veteran
Veteran of D-Day - 60 points Complete D-Day levels on Veteran
Veteran of El Alamein - 60 points Complete El Alamein levels on Veteran
Veteran of Fortress Stalingrad - 60 points Complete Fortress Stalingrad levels on Veteran
Veteran of Hill 400 - 60 points Complete Hill 400 levels on Veteran
Veteran of Rommel's Last Stand - 60 points Complete Rommel's Last Stand levels on Veteran
Veteran of Stalingrad '42 - 60 points Complete Stalingrad '42 levels on Veteran
Veteran of The Battle for Caen - 60 points Complete The Battle for Caen levels on Veteran
Veteran of The Tank Squadrons - 60 points Complete The Tank Squadrons levels on Veteran
Veteran of the Winter War - 60 points Complete Winter War levels on Veteran
War Hardened - 200 points Complete the game on Hardened or Veteran with all levels complete
Won the War - 150 points

Commisar can kill you
After you get the weapons from the table on the first stage, the comissar will tell you to shoot the teddy bears. Instead, shoot the bottles and plates -- shoot four of them, and the commisar will kill you.