Team SWAT
Team SWAT is a matchmaking playlist with the following game types: SWAT, SWAT Magnums, SWAT Oddball, SWAT Stockpile and SWAT 3 Plots. Unlike other playlists, SWAT players are devoid of all shields, grenades and sensors. This makes it much easier to pull off high CR headshots as well as increase your precision shooting ability for other playlists.
Campaign
Playing campaign also earns CR. Although you earn substantially less CR than playing online modes, it is much less competitive and opens itself to several tricks. For instance, on ONI: Sword Base, once you gain access to the airstrike gun, run into the corner as far away from any enemies as possible. You will get a checkpoint. Use the airstrike gun on the covenant nearby and immediately reset to your last checkpoint and repeat. For even more CR, play the campaign on Heroic or Legendary difficulty.
Commendations
Earning commendations is like a booster shot of CR. Throughout your Halo career you'll earn commendations from completing various accomplishments. There are several levels of commendations beginning at iron and ending at onyx. Commendations can be earned in campaign, firefight and multiplayer modes.
Challenges
Completing challenges offer some of the most CR available at once to players. Challenges change from day to day and week to week. Daily challenges typically offer about 1,000 CR for each one completed, while weekly challenges can go upwards of 11,000 CR. An easy way to earn CR for campaign challenges is to save the game just before you reach your goal for the challenge. Complete the challenge and immediately unplug the Ethernet cable from the console and exit to the menu. Plug the Ethernet cable back in and resume the game from your last checkpoint and repeat the process to continuously earn CR for the same challenge.