In case you don't want to watch the videos, here it is in text.
There are 3 Seperate killstreak tiers, you have to choose which tier you want to choose you're 3 killstreaks from but if you choose the last tier, you just get exactly what it sais.
Assault Killstreaks
4 Kills - Care Package
5 Kills - IMS - 3 or 4 placeable landmines that cannot be stunned or flashed
5 Kills - Predator Missile
5 Kills - Sentry Gun
6 Kills - Precision Airstrike
7 Kills - Attack Helicopter
7 Kills - Little Bird Flock - Mini Helicopters which patrol the map
9 Kills - Little Bird Guard - Big Helicopter that follows you from above and protects you
9 Kills - Mortar team - Mortar team but with 5 predator missiles - all go off at the same time in different places
10 Kills - Talcon - Mini Tank Robot
12 Kills - AC130
12 Kills - Pavelow
15 Kills - Juggernaught Suit - From spec Ops ( for anyone who sais in the spec ops video he gets it at 14 kills, well thats because he has hardline on)
15 Kills - Osprey Gunner Cps - You control a chopper gunner that also drops an emergency airdrop for your team mates.
Support Killstreaks
4 Kills - UAV
5 Kills - Counter UAV
5 Kills - Ballistic Duffel - Drop Juggernaught perk for the whole team, not jugg suit
5 Kills - Airdrop Trap - Drops a hacked care package
8 Kills - Sam Turret
10 Kills - Remote UAV - Target enemies with missiles
12 Kills - Advanced UAV - Blackbird
12 Kills - Remote Turret - Sentry Gun that you can control
12 Kills - Stealth Bomber
18 Kills - EMP
18 Kills - Juggernaught Recon Armour - Care Package Drop Armour
18 Kills - Escort Airdrop - Same as the Osprey Gunner but you dont control the gunner or chopper and Drops 5 care packages, one will be hacked
Specialist Killstreaks:
2 Kills - You get 1 extra perk
4 Kills - Get another perk
6 Kills - Get another perk
Yes, you do get to choose the perk you get each time.
Another thing is the killstreaks will cycle through in the same life, so you dont have to die to reset your killstreaks and get your first killstreak again.
DeathStreaks
Juiced - Lightweight - 4 Deaths
Martyrdom - 4 Deaths
Final Stand - 4 Deaths
Revenge - Last person that killed you is always visible on your mini map - 5 Deaths
Stopping power for one kill - 5 Deaths
Dead Mans Hand - You run around with c4 in your hand (suicide bomber) - 6 Deaths
Perks
Plus = With Pro added
Tier 1
Extreme Conditioning - Sprint longer distances + Climb obstacles faster
Sleight Of Hand - Reload faster + Faster weapon swapping
Scavanger - Reload ammo from bags + Spawn with more ammo
Blind Eye - Undetectable from air support + Faster launcher lock on and extra damage to air support
Recon - Explosive damage marks target on HUD + Bullet damage marks target on HUD
Tier 2
Hardline - One less kill for Killstreak + Two assists count as a kill towards next killstreak
Assassin - Immune to UAV, Motion Sensor, Thermal and Heartbeat Sensor + Immune to CUAV & EMP
Overkill - Two primary weapons + Second primary can have 2 attachments
Quickdraw - Faster aim down sights + Faster animation of using equipment and throwing grenade
Blastshield - Flack Jacket (Immune to most explosives) + Immune to stuns and flashes
Tier 3
Sitrep - Enemy equipment is visible + Enemy footsteps are more clear
Dead Silence - Your footsteps are silent + No fall damage
Stalker - Faster movement with ADS + Delay on claymores
Marksman - ID target from range + Longer hold breath on scoped weapons
Steady Aim - Increased hip fire accuracy + Faster aim down sight while sprinting