A kill streak is the number of kills a player is able to achieve without dying. Typically, kill streaks are found in multiplayer games, and often trigger rewards for players,
Kill streaks were popularized in the Call of Duty series, particularly Call of Duty 4: Modern Warfare. This game rewarded the player with an Unmanned Aerial Vehicle that provided radar after 3 kills, an Airstrike bombing run after 5 kills, and a helicopter that fired on enemy players after 7 kills.
Kill streaks have become increasingly popular and widely expanded. For example, Call of Duty: Modern Warfare 2 allows the player to choose from a variety of kill streaks, each requiring a different amount of kills and offering varying rewards.
Kill streaks as they are known today have grown out of more humble, but closely related, beginnings. For example, many early turn based strategy games allowed for players to slightly power up their units by scoring killing blows in succession. Also, some early brawler games rewarded players with a score multiplier that increased with each kill in rapid succession. Even sports games such as NBA Jam incorporated a reward for a player that made three successive baskets without any interruption.
These early examples, however, were more like combos for scoring purposes. First person shooters began to more fully explore and embrace this distinction, and also began moving away from the time proximity requirement, and instead into per life requirement.
Kill streaks can serve a variety of purposes. Some offer tangible rewards, some offer score based awards, and some are purely for bragging rights.
Probably the best known example of kill streaks is the Call of Duty series. In Call of Duty, kill streaks result in the aptly named Kill Streak Reward. This is a tangible benefit that is applied to either your own team, or the detriment of the opposing team. These kill streaks also work in Free for All matches.
There kill streaks work to encourage the player to play well, and then provide a further reward for doing so. One added effect of such kill streaks is that they prevent "Body Tossing" techniques. In online multiplayer games, it is so easy to respawn that some of the inherent tension may be lost. By increasing the reward for staying alive, kill streaks help add more tension to the gameplay.
Score rewards are kill streaks that increase the player's points. These often come in the form of multipliers or combos. For example, Madballs: Invasion has a system where kills result in multiplier pick ups. A player's multiplier then drops according to time, damage taken, and death. Therefore, a player that stay alive, and manages to score several kills, will find their kills more valuable than a player who dies in between each kill.
Score rewards are a slightly more passive form of kill streak than tangible rewards. They do encourage a certain type of play, and reward skillful play, but a player can more or less ignore them and still get full enjoyment of the game. Score type kill streaks may also award the player with more experience towards a leveling system, unlocking new equipment or levels faster.
Other Kill Streaks
Games such as the Halo: Combat Evolved have kill streaks that are purely for bragging rights. In Halo: CE, a player could earn a double kill, triple kill, or killtacular by getting 2, 3 and 4 kills in quick succession. These kill streaks did not provide the player with a reward other than the voice over announcer stating the streak occurred, and a message appearing in the kill feed.
These kill streaks do not provide any reward to the player other than for bragging rights or a personal sense of accomplishment. They are, by far, the most passive of kill streaks. While a player may attempt to complete them, a player could completely ignore them and still get a full game experience.
While most would agree that kill streaks are an interesting addition to gaming, there are some serious drawbacks. One is the potential to encourage camping style gameplay. A "camper" tries to hole up in an easily defensible position in order to prevent deaths. This slows the gameplay down, and many other players find it takes away from the overall experience. Kill streaks, which reward kills without deaths, can encourage camping. It should be noted that campers can usually be countered by a skillful player.
Kill streaks may also encourage other tactics that may ruin the game experience for other players. Some players will deliberately use only the strongest weapons in order to try to get high kill streaks. This is a problem inherent to any competitive gameplay, however, and not entirely dependent on kill streaks.
Kill streaks can be prone to abuses as well. For example, in Call of Duty: World at War, it was discovered that upon getting 7 kills without dying, one could call in a pack of dogs to attack their enemies. This powerful kill streak could be abused if the player died before using the kill streak, as on their respawn they could call in the dogs. The dogs kills would then be added to their next kill streak, meaning once a player reached 7 kills, they would often suicide, use their dogs to get 7 kills, suicide, and repeat.
Additionally, people attempting to get the Tactical Nuke kill streak in Modern Warfare 2 will sometimes act inchoate to arrive at a 25 kill streak simply by allowing one player to kill the other repeatedly.