Perks were added to the newest update for the iOS version of SAS: Zombie Assault 3, and they are exclusive to this version as well. Perks give the players an advantage in-game by giving them special abilities and enhancements for their character. They only last for the duration of one game however. Before entering any game, the perk selection screen will appear, which is where you can spend in-game money to activate any number of perks. The effects of some perks are stackable. This means that in in Co-Op mode, if any other players have purchased the same stackable perk as you, the in-game bonus of the perk will be multiplied accordingly.
Weapons Specialist (Cost = $ (120xlevel) ) - Gives you five GECAL 50 Sentry Guns and five Area Denial Weapon Systems, and all sentry guns do 25% bonus damage (Stackable)
Sharpshooter (Cost = $ (30xlevel) ) - Increases base weapon damage by 25%. (Not Stackable)'
Officer (Cost = $ (30xlevel) ) - Increases the base damage of guns, grenades and sentry guns for all players by 15%. (Stackable)'
Super Solider (Cost = $ (30xlevel) ) - Increases your HP by 50%. When your HP falls below 10% for the first time, you will recover all of your health and receive double damage for 30 seconds. (Not Stackable)
Combat Medic (Cost = $ (40xlevel) ) - Gives all players a small health regen rate and a 25% faster revive. (Stackable)
Combat Engineer (Cost = $ (10xlevel) ) - Makes all barricades 75% tougher. (Stackable) In addition, barracides fixed by people who have purchased this perk will be 500% stronger. (This effect of the perk is not stackable)
Science Corps (Cost = $ (60xlevel) ) - You will get an 8% chance to freeze a zombie for 0.7 seconds with weapons and a 30% chance to freeze a zombie when one hits you. (Not Stackable)
Grenadier (Cost = $ (60xlevel) ) - Gives you ten Frag Grenades, five Cryo Grenades and one Holy Grenade. It also increases the damage of all grenades by 25%. (Stackable)
edit/fix by Raziel (not signed up for wikia)