Emblems

Emblems, first introduced in Halo 2, are small designs that are associated with a Character Profile and used to represent a player's identity in multiplayer games and online play. They consist of a two-colored design or pattern overlaid upon a background (typically a geometric shape), with a user-selected color scheme applied to the result. The feature was later carried on into Halo 3 and Halo 3: ODST.

Halo 2 Emblems
In Halo 2, when a Character Profile is created, there is an option to make an Emblem for your character. Emblems are the primary means of identifying players in multiplayer games and online play; they also appear in the game type Territories, where they are displayed on the flags that denote captured territories. The color and background of the emblems are usually determined by the primary and secondary armor colors. In-game, a player's emblem can be seen glowing on their back and shoulders.

Halo 3 Emblems
Emblems also appear in Halo 3. All of the designs from Halo 2 (except for Sergeant, Waypoint, Cleave, and Race) are available, along with numerous new designs unique to Halo 3. The background shape's color is now determined by a third, user-selected color, as opposed to Halo 2, where it took on the same color as the player's armor. Also, in Halo 3, a design can be "toggled" -- the secondary Emblem color can be hidden.

Emblems in Halo 3 are less prominent than they were in Halo 2; in Halo 3, a Spartan player's emblem is only shown on their right shoulder, whereas in Halo 2, it could be seen on both shoulders and the player's back. Elite players' emblems are shown on their right shoulder and upper back. Emblems are no longer used to uniquely identify a player; that job has been taken on by a new, user-customizable call sign composed of a letter followed by two digits.

Some clans encourage their members to use the same emblem to signify unity; in such cases, the emblem functions similarly to a US Army Shoulder Sleeve Insignia.

The 80 primary emblem designs, the 80 "toggles" of those designs, the 48 possible emblem backgrounds, and the 30 possible colors for each of the above all allow for a combined total of 9,216,000 possible Emblems in Halo 3.

Halo 3: ODST Emblems
Emblems are also featured in Halo 3: ODST Firefight mode. All Emblem designs from Halo 3 (including Pirate, Bubble Shield, and Trip Mine) are available, along with numerous new designs unique in Halo 3: ODST. Emblem designs appear on the player's chest plate.

Halo: Reach Emblems
It has been confirmed that emblems will be returning in Halo: Reach. Emblems are featured in the Multiplayer Beta as well. Three new designs are featured in Halo: Reach after Bungie held a contest where players could send in their ideas for emblem designs, similar to the contest that was held before Halo 3 was released. Several, if not all, emblems from Halo 3: ODST return such as the ONI symbol. List of confirmed new emblems:
 * Human skull with bullet through head.
 * Cone.
 * "No Camping"; Tent with a cancel sign over it.
 * Joker playing cards.

Trivia

 * You can "toggle" a design by pressing X while modifying your emblem's design, background, or colors; doing so hides all portions of the Emblem that use the secondary emblem color.
 * Some players have formed unique emblems by toggling the designs. As an example, toggling the Grunt design and using the Arrow background makes "The Bat". On a similar note, a chicken can be created by using a Bullseye with the Ball of Fire.
 * Toggling the Seventh Column design makes it completely invisible, as the entire design is shown using the secondary emblem color. This, in combination with the Blank background, makes it possible to have a completely transparent emblem.
 * The Bubble Shield and Trip Mine emblems return in Halo 3: ODST and Halo: Reach, despite the player not using Equipment in ODST while playing as an ODST. These emblems probably returned due to the fact that Brutes can still carry and use them. These emblems return in Halo: Reach, despite the fact that Equipment has been replaced with new Armor Abilities.
 * The Marathon symbol is available as an emblem in Halo 2, Halo 3, and in Halo 3: ODST.
 * Prior to Halo 3 's release, Bungie held a contest in which people could send in their ideas for Emblem designs. The Pirate Emblem was the winner, and can be used in Halo 3, Halo 3: ODST, and Halo: Reach.
 * The three Spartans from Red Team in Halo Wars have emblems from Halo 3 and are also the first characters to use emblems in Campaign.
 * Emblems, when shown on a player's armor, are most prominent on a Spartan CQB Right Shoulder armor part.
 * In Halo 3: ODST, one of the many new emblems added is the seal of the rampant UESC AI Tycho. Tycho's seal is the second emblem to be added to the list that makes reference to Bungie's previous game, Marathon.