Hardline- Killstreaks require 1 less kill (Very useful, more than it sounds)
Last Stand- Go into last stand mode after death. You can crawl slightly.
One Man Army- Awesome perk, find out for yourself =P

There are several guns in the game. AK-47 is actually the last assault rifle you unlock in the game. You get the Barrett 50. cal right off the bat at lv 1. Instead of there being a 1 handgun side-arm, you can now choose from several side-arms. No perks needed. You get 1 primary weapon. 1 secondary weapon. 1- Equipment. 1-for each perk 1-3. And 1 deathstreak perk. A dathstreak perk is a perk that activates when youre not doing so well. After you die without getting kills a few times, your deathstreak perk activates. One of the perks is copycat. You copy the perks of the person that killed you. He/She could be lv 75 with awesome pro perks, and a lv 1 n00b could copy them =D

Here are the Secondary weapon categories. Primary weapon categories are same as usual.
Automatic Handguns
Shotguns
Launchers
Handguns
Dont look forward to the magnun this time ppl, it sucks...

Here is some equipment you can get
Blast Shield(weakens explosive damage)
Frag-duh
semtex-sticky grenade
Throwing knife- knife like in 007. You can throw it to kill, then pluck it out of your enemie's body to use over an over again =D

There are several maps. Some snowy, some urban, some gritty, some chaotic. You'll have fun.

Here are some tips for success.
Dont use the Tac Nuke killstreak unless your like COD GOD or something. I've only used it once so far, not worth it. Best killstreak setup is Precision Airstrike, Sentry gun, and self-piloted helicopter (cobra) the airstike is like the old ones, except you can target a direct line after the initial strike to spread the bombing outwards. Sentry gun gets lots of kills if used right. You can pretty much set up a computer piloted turret anywhere on the map. put it in the middle of a busy area and you can be rolling in the kills.