There are three slots and by default, you can get only one perk per slot. However, if the need be, then you can opt for ‘wildcards’, which allows you two perks in one slot.
Note that this will consume more of your allocation points, which could otherwise be used on weapon attachments and other equipment.
There are no Pro Perks in Black Ops 2 and perks don’t enhance your weapon either; you have to use weapon attachments for better weapon stats.
Perks For Slot 1
Blind Eye: AI controlled Scorestreaks don’t target you. However you are targetable once the player takes manual control.
Flak Jacket: Increased resistance against explosions meaning you take less damage from grenades and bombs.
Ghost: UAVs don’t detect you as long as you keep moving.
Hardline: Gives you extra points on objectives allowing you to get Scorestreaks rewards faster.
Light Weight: Increased movement speed and you take no damage from falls.
Perks For Slot 2
Cold Blooded: You cannot be targeted by enemy targeting technology such as Dual Band, Sensor Grenade, Target Finder, etc.
Fast Hands: You can swap weapons faster. Equipment and grenades can also be used faster which means you can throw back enemy grenades more effectively.
Hardwired: You aren’t affected by Counter UAV’s and EMPs. However, even thought the EMP doesn’t affect you, you still can’t use Scorestreak rewards.
Scavenger: Enemies leave behind Scavenger bags which contain ammo and grenades.
Toughness: Reduces flinching when shot.
Perk Slot 3
Awareness: Makes enemy movement and noise four times louder.
Dead Silence: Reduces noise made by your movement.
Dexterity: You can get over obstacles and climb ladders faster. Also makes you recover faster from melee attacks and allows you to aim shortly after sprinting.
Engineer: You can see enemy equipment through walls. Also delays enemy traps triggered by you.
Extreme Conditioning: Allows you to sprint continuously for twice the distance you did before.
Tactical Mask: You are affected less by Flash Grenades, Concussion Grenades and Shock Charges.