All 25 perks in Aisle Zero, by rarity
Every perk you can be offered between waves, what it does and how many times you can take it.
Between waves the game offers you a choice of perks. There are 25 in total: 4 common, 8 uncommon, 6 rare, 4 epic, 3 legendary.
Stacking
Most perks can be taken more than once. The stack limit on each card is the ceiling — some go as high as nine, others can only be taken once.
Rarity
Rarer perks are offered less often and tend to do more when they appear. That does not make them automatically correct: a common perk taken five times often beats a legendary taken once.
Perks and God Mode
Certain perk and weapon combinations unlock a hero's God Mode. If you are building towards one, the perk screen stops being a menu and starts being a checklist — see God Mode explained.
The full list
Every perk has its own page with its effect in the game's own words. Browse them all on the perk list.