Currently the game has 5 different power-ups. All power-ups have a different effect, but ultimately they make you more competitive against your opponents by making your birds stronger or more accurate or even by shaking the earth itself!
Wingman: The Wingman is a super-powered bird that you can call upon when you need to deal out some extra destruction in Angry Birds Friends. You can summon the Wingman by clicking the Wingman icon in the right edge of the power-up menu. The Wingman will then replace whichever bird is currently in the slingshot.
Birdquake: The Birdquake is a power-up that shakes the ground in any level. It is best used for nudging pigs off of ledges and bringing unstable buildings crumbling to the ground.
Sling Scope: The Sling Scope is a power-up that allows you to see the bird's trajectory before launch. Once activated, the Sling Scope will remain on the slingshot until you complete, retry, or exit the level.
King Sling: The King Sling is a power-up that increases the initial launch speed of all your birds. This directly increases the amount of damage all your birds do and changes their flight trajectory.
Power Potion: The Power Potion is a power-up that increases the size of the bird that is currently in the slingshot. This directly increases the amount of damage the bird does.