Private match player pool

Playing online against other human opponents is intimidating in games as competitive as the Call of Duty series, but you can practice your skills against bots in the Combat Training mode. Learn the maps, learn the weapons, and kill AI-controlled opponents named after people on your Steam friends list... which is a nice touch. You can also set up a private server with any manner of game modes and modifiers if you just want to have some fun. These options aren't ranked, naturally, but they still provide players with a closed off area to mess around with the game.