Rewarding players on an individual basis, killstreak rewards, as well as a team basis, team score, is an interesting concept.
Halo 2 had many ways to interact with the maps in the form of gates, bridges, stalactites and more.
By marrying these two concepts, rewarding individual players for killing AND interacting with the map to gain an advantage, Halo can embrace its own version of killstreak style rewards.
Killing enemies builds up a personal score that is used as currency. Maps contain items like gates, light bridges, shield doors, mancannons, teleporters, turrets, laser arrays, electromagnetic land mines and more. These items are powered down until a player spends currency to activate them for a finite time period. A strategically located turret can give the player an advantage in Slayer games. An extendable bridge can give the flag carrier an advantage in CTF. Closing a gate can aide defenders in Assault.
Map control is enhanced by this relationship, killing then choosing a reward by going to a specific location on the map, because it allows players to choose how they want to position themselves in regard to their objective (slaying, attacking, defending, etc), their current amount of currency (how many enemies they've killed), and their plan for that currency (which Interactive Map Item they will purchase and when).
What do you think? Any ideas for your own Interactive Map Item?