Multiplayer

The online multiplayer mode of Black Ops retains the experience points and unlockable reward system that has been kept since Call of Duty 4. The game's multiplayer focuses on socialization and customization. "Create-a-Class 2.0" allows enhanced personalization with appearance items as well as upgradable perks; weapons are extensively customizable with writing, emblems, attachments and camouflage painting. Even reticles can be modified. There are more than one style for an attachment, which allows for a lot more personalized weaponry; for example, the player can choose between a red dot sight or a reflex sight, both of which share the same traits, they merely look different. Character models depend on the first tier perk instead of the weapon's type. Furthermore, face paints can be unlocked. New custom killstreak rewards include explosive R/C cars, guided missiles and controllable attack helicopters.

A currency system has been implemented allowing players to buy weapons, accessories and clothes. Players can gamble with their "COD Points" in a free-for-all based playlist called "Wager Match", which is composed of four game modes. Time limited objectives known as "Contracts" can be purchased to gain more currency and experience points. The progression system is not featured in local split-screen multiplayer. In local split-screen play, all character customization options are already unlocked. Players can no longer define game rules such as win conditions.

Players can play alone or with friends against AI opponents in "Combat Training" with a separate progression system. Online split-screen is re-introduced on Xbox 360 and PS3. The guest account can rank up but is reset after each sign out. Only on Xbox 360, a second Gold Xbox Live account can be used to keep the second player's progression.

For the first time in the series, clips from online gameplay can be recorded. Some specific features that have been removed from the PC version of Infinity Ward's Modern Warfare 2 return, such as lean, mod tools, the developer console and dedicated servers. Dedicated servers are exclusively provided by Game Servers. Steam is the exclusive platform for Black Ops on PC, and the game is protected by Valve Anti-Cheat.

The Wii version of the game includes in-game voice chat. This is the first Call of Duty title to include the voice chat feature for the Wii. Nintendo and PDP have partnered to release the first headset to be used with the Wii known as PDP's Headbanger Headset.

Source: http://en.wikipedia.org/wiki/Call_of_Duty:_Black_Ops#Multiplayer