Your killstreak is determined by how many people you kill without dying. In Call of Duty 4 Modern Warfare, it is possible to get an unlimited killstreak if time is applicable.
There are only three killstreak rewards. They are as follows:
Effects of killstreak rewards:
Yes they do.
The yellow bar is how many kills you got towards your kill streaks.
harrier ac130 and nuke
Chopper Gunner, Predator Missle, Harrier Airstrike.
kill heaps of enemy killstreaks
lvl up till you get a killstreak token or something go onto assualt killstreaks - care package (you must be using assault killstreaks support drops a fake one that blows up)
Killstreaks in MW2 are tools, such as Predator Missiles, that can help you eliminate your enemies easily. If you have a Killstreak but you are killed, you will have to start the streak again but you will keep any killstreaks unlocked.
UAV, Airstrike, Helicopter (not drivable, it just flys around the map)
More guns. It continues the storyline from modern warfare 2. For multiplayer, there will be more perks and killstreaks and weapons. Also for multiplayer there will be more maps.
The best killstreak is the Tactical Nuke but use killstreaks that you can get frequently.
so far it is unown, but i heard there wil be a helecopter version of the RC car
there arent any
You mean the Infinity Ward emblem? Complete the "Wargasm" challenge by getting all of your killstreaks within 20 seconds. Quite easy with Hardline and the lowest killstreaks.