Prestige

In Call of Duty: Black Ops, players are able to enter Prestige Mode at the highest rank of 50. The maximum number of Prestige levels is 15.

pros: 

The player gets to keep their emblems, backgrounds, and game modes. The player gains new custom classes, new playercard images, and more challenges. The player used to gain access to certain lobbies in the Prestige playlist, but this has been deleted as very few players used it.

cons:

The player's COD Points balance prior to prestiging will be reset to 0. Again, all challenges completed, weapons unlocked, and Pro perks earned will be reset. Similar to the Veteran challenges from Modern Warfare 2, however, Lifetime Challenges are not reset upon Prestiging.
Picture

entering prestige mode

When the "Prestige Mode" button is clicked, a message appears, with the words:

"Trade all your accomplishments for a bit of prestige. Other players will see your new prestige rank in the lobby, leaderboards and game."

or (Call of Duty: Modern Warfare 2 only)

"Trade all your accomplishments for a bit of prestige. In addition to your new prestige rank icon, you'll gain access to some new titles, emblems and challenges. Other players will see your new prestige rank in the lobby, leader boards and game."

After this message the player can select "More Info" or cancel and return to the menus. After clicking "More Info", a second warning appears:

"Prestige has a price: Everything you've unlocked including weapons, experience and challenges will be reset; you'll have to rank up again to reacquire them. Only your leader board rankings, clan tag, and play lists will be unaffected."

or (Call of Duty: Modern Warfare 2 only)

"Prestige has a price: Everything you've unlocked including weapons, experience and challenges will be reset; you'll have to rank up again to reacquire them. Only your Leaderboard rankings, titles, emblems, clan tag, and playlists will be unaffected."

Should the player still be determined to go to Prestige Mode, one final warning is shown:

"There's no going back..."

Should the player then hit "Enter Prestige", the decision is final and Prestige Mode is activated. In Call of Duty 4: Modern Warfare, a Desert Eagle shot is heard to confirm it. In Call of Duty: Modern Warfare 2, when the player enters this message, a Claymore will tick. If the player decides to press Cancel, they will hear a Chicken clucking, most probably to mock the player for chickening out of Prestiging at the last moment. If they continue, the Claymore will blow up.