Medal

In the multiplayer mode of Call of Duty: Black Ops II, Call of Duty Online, Call of Duty: Advanced Warfare, and Call of Duty: Black Ops III, medals are rewarded for different accomplishments. These accomplishments can range from securing flags and bombs in objective game modes to getting an exceptional amount of kills in a single life. Each medal, including duplicates, provide bonus XP, which is displayed in the After Action Report at the end of the match.

Kill Medals
Kill Medals are rewarded whenever a player kills an enemy under circumstances different from a regular kill. This can include killing an enemy before they can kill a teammate, awarding the Savior medal, or killing an enemy that has killed the killer before, awarding the Revenge medal. They are also rewarded with unconventional weapons and equipment, such as the Combat Axe and the Ballistic Knife.

Killstreak Medals
Killstreak Medals are rewarded for going on a killstreak (multiple kills in a single life). Scorestreaks do not contribute to this streak; only kills from weapons, the knife, lethals, tacticals and environmental (such as cars and barrels) are counted. Medals scale until the 31st kill, at which point each non-scorestreak kill will be rewarded with the Unstoppable medal.

Rapid Kill Medals
Rapid Kill Medals are awarded for killing multiple enemies in a certain timeframe. Unlike previous games, the timeframe to achieve these kills is much larger, and each kill extends the time to achieve the next. As with the Killstreak Medals, scorestreak kills do not contribute to this. Even if the player were to manage continuing their streak soon enough, dying ends the timeframe. Rapid kills contributes, as well, for unlocking titles.

Scorestreak Medals
Scorestreak Medals are rewarded for getting direct kills on enemy players from scorestreaks. Due to this, it is impossible to get medals from support scorestreaks such as the UAV. Medals stack, meaning that multiple medals can be awarded from a single scorestreak. Example: a double kill from a Hunter Killer will award two Bullseye medals.

Scorestreak Destroy Medals
Scorestreak Destroy Medals are rewarded for destroying enemy scorestreaks. This can be done in a variety of ways, be it from using the FHJ-18 AA on a Counter-UAV, to using the Black Hat PDA on a Guardian, or even an EMP (grenade or scorestreak) on any of the scorestreaks. Destroy medals are visually similar to their scorestreak counterparts, but have a dark red background instead of a gold one.

Playlist Medals
Playlist Medals are rewarded in different game modes when certain parameters of obtained, such as capturing flags in Domination or defusing bombs.

Objective Medals
Objective medals offer some of the highest XP rewards in the game, incentivising objective play when applicable.

'NB: "Any objective game mode" relates to any game mode with a static objective or objective location. To this end, it does not include Kill Confirmed.'

Party Game Medals
Party Game Medals appear exclusively in the Party Games playlist. They are rewarded from various achievements, such as getting the most kills within a gun rotation in Sharpshooter, or quickly moving up a rank in Gun Game.

End of Match Medals
End of Match Medals are rewarded for finishing any public match.

Miscellaneous Medals
There are additional medals that are not rewarded for any of the above reasons, and revolve more around the metagame of stealing, sharing and hacking.

Call of Duty: Online
Medals return in Call of Duty Online much like its Black Ops II counterpart.

Kill Medals
Kill Medals are rewarded whenever a player kills an enemy under circumstances different from a regular kill much as they are in Call of Duty Black Ops II, however they are more closely based off the Call of Duty: Modern Warfare 2 callouts.

Killstreak Medals
Killstreak Medals are rewarded for going on a killstreak (multiple kills in a single life). Scorestreaks do not contribute to this streak; only kills from weapons, the knife, lethals, tacticals and environmental (such as cars and barrels) are counted. All medals use the same icon however the text description underneath will be all that is different. They are awarded at 5, 7, 10, 15, 20 and 25 kills. Every kill after the 26th kill will use the Unstoppable description.

Rapid Kill Medals
Rapid Kill Medals are awarded for killing multiple enemies in a certain timeframe. As with the Killstreak Medals, scorestreak kills do not contribute to this.

Miscellaneous Medals
There are additional medals that are not rewarded for any of the above reasons, and revolve more around the metagame of stealing, sharing and hacking.

Call of Duty: Advanced Warfare
Medals were seen in the campaign trailer for Call of Duty: Advanced Warfare. "Skeet Shooter" appears after the player kills an enemy while they are jumping.

Trivia

 * In Black Ops II, as of patch 1.06, all gunstreak medals have been given a different design.
 * In Black Ops III, many Scorestreak medals depict a model of the Scorestreak from Black Ops II.