The following perks have the corresponding effects:

PERK - EFFECT
Marathon - Unlimited sprint.
Sleight of Hand - Faster reloads.
Scavenger - Resupply from dead enemies.
One Man Army - Change classes at anytime at the loss of a secondary weapon.
Stopping Power - Increase bullet damage against enemy players.
Lightweight - Move quicker.
Hardline - Killstreaks require one less kill.
Cold Blooded - Undetectable by UAVs, air support, sentry guns and thermal vision.
Danger Close - Increased explosive weapon damage.
Commando - Increased melee distance.
Steady Aim - Increased hip-fire accuracy.
Scrambler - Jams enemy radar near you.
Ninja - Invisible to heartbeat sensors.
SitRep - Detect enemy explosives and tactical insertions.
Last Stand - Fall to the ground and use your secondary weapon until you bleed out.
Bling - Two primary weapon attachments.