Perk Slot 1
Lightweight | Lightweight Pro
Ability: Allows you to move faster, but how fast depends on the equipped weapons mobility. This should be used with a "run and gun" class due to the added speed.
Pro Ability: No falling damage.
Scavenger | Scavenger Pro
Ability: Replenishes your ammunition and lethal grenades when you walk over blue scavenger bags that are dropped by dead players. This won't resupply launchers or equipment. Scavenger is very useful with weapons that run out of ammo quickly.
Pro Ability: Doubles your starting ammo with extra magazines. This also replenishes your tactical grenades.
Ghost | Ghost Pro
Ability: Ghost works pretty much like Cold Blooded from Modern Warfare 2, but it doesn't make you invisible to infrared scopes. You are undetectable by the Spy Plane and Blackbird killstreaks when you have this equipped. You only show up on the radar if you fire a weapon that doesn't have a silencer.
Pro Ability: Undetectable by aircraft, dogs, infrared and sentries. Enemies won't see your name or a red crosshair when targeting you.
Flak Jacket | Flak Jacket Pro
Ability: Flak Jacket greatly reduces explosive damage and allows you to survive any indirect explosive attack. Explosive crossbow bolts are lethal if they get stuck on you and explode.
Pro Ability: Immune to fire damage and allows you to reset the fuse of a thrown grenade when you pick it up.
Hardline | Hardline Pro
Ability: Reduces the amount of kills required for any killstreak by one. For example, the Care Package normally requires 5 kills, but if you have Hardline equipped you only need 4 kills.
Pro Ability: Allows you to randomly choose another reward from a Care Package. When you open a Care Package, you can either take the reward or try again for something better.
For example, when selecting a Care Package and you get the Spy Plane killstreak reward, you get the following option: "Hold X for Spy Plane OR Double Tap to Try Again" (Xbox 360)
Perk Slot 2
Hardened | Hardened Pro
Ability: Increases your weapons bullet penetration, but it doesn't increase bullet damage. This is pretty much like Deep Impact from Call of Duty 4 and FMJ weapon attachment from Modern Warfare 2.
Pro Ability: Your weapons do extra damage to aircraft and turrets. This also reduces flinch when you are shot by someone.
Scout | Scout Pro
Ability: Enables you to hold your breath longer when steadying a weapons scope. Scout offers a significant advantage to sniper class weapons.
Pro Ability: Allows you to switch your weapon faster.
Steady Aim | Steady Aim Pro
Ability: Steady Aim increases a weapons hip fire accuracy and also reduces shotgun spread. This should be used with the Dual Wield attachment, since Dual Wield significantly reduces a weapons hip fire accuracy.
Pro Ability: When equipped, this enables you to fire faster after sprinting and recover faster from a knife lunge.
Sleight of Hand | Sleight of Hand Pro
Ability: Gives a faster reload time by reducing your weapons reload time in half. This is extremely useful with weapons that have long reload times, like shotguns and light machine guns.
Pro Ability: Allows you to aim down the sight ~50% faster than normal. This doesn't work with weapons that have scopes.
Warlord | Warlord Pro
Ability: This is the equivalent of Bling from Modern Warfare 2. Warlord allows you to put 2 attachments to your primary weapon. Stealth classes should use this since they can equip a silencer to remaining undetected and still reap the benefits of having a second attachment.
Pro Ability: You start with one extra lethal and tactical grenade, except smoke.
Perk Slot 3
Marathon | Marathon Pro
Ability: This extends your sprint time, but it doesn't increase your speed.
Pro Ability: Gives you unlimited sprint.
Ninja | Ninja Pro
Ability: Ninja allows you to walk, sprint and jump almost silently, therefore you can sneak behind enemies more easily. This is the equivalent of Dead Silence from Call of Duty 4.
Pro Ability: When you have this equipped enemies will be louder, it also makes you completely silent.
Second Chance | Second Chance Pro
Ability: Gives you the ability to survive a normal death by dropping you to the ground. You can use your pistol to defend yourself from enemies. Second Chance ends after 10 seconds or if you take a single hit from the enemy, and in both cases, you will die.
Pro Ability: If you have Second Chance Pro equipped you can survive a little longer. Teammates can also revive you - even players that don't have Second Chance. You can see a white REVIVE tag above a player that can be revived.
Hacker | Hacker Pro
Ability: Allows you to see enemy explosives, equipment and Tactical Insertions. This highlights them with a red color like SitRep from Modern Warfare 2.
Pro Ability: This is one of the most interesting additions to the whole Black Ops perks list. Hacker Pro actually allows you to sabotage enemy Care Packages and also turn enemy equipment friendly. This also makes you invisible to Motion Sensors.
Tactical Mask | Tactical Mask Pro
Ability: Protects you against gas grenades.
Pro Ability: Tactical Mask Pro reduces the effects of flashbangs and concussion grenades, it also reveals the position of a flashed or stunned enemy.
Source: http://www.cod7blackops.com/
Lightweight | Lightweight Pro
Ability: Allows you to move faster, but how fast depends on the equipped weapons mobility. This should be used with a "run and gun" class due to the added speed.
Pro Ability: No falling damage.
Scavenger | Scavenger Pro
Ability: Replenishes your ammunition and lethal grenades when you walk over blue scavenger bags that are dropped by dead players. This won't resupply launchers or equipment. Scavenger is very useful with weapons that run out of ammo quickly.
Pro Ability: Doubles your starting ammo with extra magazines. This also replenishes your tactical grenades.
Ghost | Ghost Pro
Ability: Ghost works pretty much like Cold Blooded from Modern Warfare 2, but it doesn't make you invisible to infrared scopes. You are undetectable by the Spy Plane and Blackbird killstreaks when you have this equipped. You only show up on the radar if you fire a weapon that doesn't have a silencer.
Pro Ability: Undetectable by aircraft, dogs, infrared and sentries. Enemies won't see your name or a red crosshair when targeting you.
Flak Jacket | Flak Jacket Pro
Ability: Flak Jacket greatly reduces explosive damage and allows you to survive any indirect explosive attack. Explosive crossbow bolts are lethal if they get stuck on you and explode.
Pro Ability: Immune to fire damage and allows you to reset the fuse of a thrown grenade when you pick it up.
Hardline | Hardline Pro
Ability: Reduces the amount of kills required for any killstreak by one. For example, the Care Package normally requires 5 kills, but if you have Hardline equipped you only need 4 kills.
Pro Ability: Allows you to randomly choose another reward from a Care Package. When you open a Care Package, you can either take the reward or try again for something better.
For example, when selecting a Care Package and you get the Spy Plane killstreak reward, you get the following option: "Hold X for Spy Plane OR Double Tap to Try Again" (Xbox 360)
Perk Slot 2
Hardened | Hardened Pro
Ability: Increases your weapons bullet penetration, but it doesn't increase bullet damage. This is pretty much like Deep Impact from Call of Duty 4 and FMJ weapon attachment from Modern Warfare 2.
Pro Ability: Your weapons do extra damage to aircraft and turrets. This also reduces flinch when you are shot by someone.
Scout | Scout Pro
Ability: Enables you to hold your breath longer when steadying a weapons scope. Scout offers a significant advantage to sniper class weapons.
Pro Ability: Allows you to switch your weapon faster.
Steady Aim | Steady Aim Pro
Ability: Steady Aim increases a weapons hip fire accuracy and also reduces shotgun spread. This should be used with the Dual Wield attachment, since Dual Wield significantly reduces a weapons hip fire accuracy.
Pro Ability: When equipped, this enables you to fire faster after sprinting and recover faster from a knife lunge.
Sleight of Hand | Sleight of Hand Pro
Ability: Gives a faster reload time by reducing your weapons reload time in half. This is extremely useful with weapons that have long reload times, like shotguns and light machine guns.
Pro Ability: Allows you to aim down the sight ~50% faster than normal. This doesn't work with weapons that have scopes.
Warlord | Warlord Pro
Ability: This is the equivalent of Bling from Modern Warfare 2. Warlord allows you to put 2 attachments to your primary weapon. Stealth classes should use this since they can equip a silencer to remaining undetected and still reap the benefits of having a second attachment.
Pro Ability: You start with one extra lethal and tactical grenade, except smoke.
Perk Slot 3
Marathon | Marathon Pro
Ability: This extends your sprint time, but it doesn't increase your speed.
Pro Ability: Gives you unlimited sprint.
Ninja | Ninja Pro
Ability: Ninja allows you to walk, sprint and jump almost silently, therefore you can sneak behind enemies more easily. This is the equivalent of Dead Silence from Call of Duty 4.
Pro Ability: When you have this equipped enemies will be louder, it also makes you completely silent.
Second Chance | Second Chance Pro
Ability: Gives you the ability to survive a normal death by dropping you to the ground. You can use your pistol to defend yourself from enemies. Second Chance ends after 10 seconds or if you take a single hit from the enemy, and in both cases, you will die.
Pro Ability: If you have Second Chance Pro equipped you can survive a little longer. Teammates can also revive you - even players that don't have Second Chance. You can see a white REVIVE tag above a player that can be revived.
Hacker | Hacker Pro
Ability: Allows you to see enemy explosives, equipment and Tactical Insertions. This highlights them with a red color like SitRep from Modern Warfare 2.
Pro Ability: This is one of the most interesting additions to the whole Black Ops perks list. Hacker Pro actually allows you to sabotage enemy Care Packages and also turn enemy equipment friendly. This also makes you invisible to Motion Sensors.
Tactical Mask | Tactical Mask Pro
Ability: Protects you against gas grenades.
Pro Ability: Tactical Mask Pro reduces the effects of flashbangs and concussion grenades, it also reveals the position of a flashed or stunned enemy.
Source: http://www.cod7blackops.com/