Cards are varying use rates. This list represents their userates from 1v1. This means ladder from 0 trophies to the Top 200.
There are going to be 4 tiers that have cards. The first one is OverUsed (OU) which has cards that have a 10% or higher use rate. The second one is UnderUsed (UU) with a userate that is lower than 10% but equal or higher than 5%. Next is NeverUsed (NU) with lower than 5% but equal or higher than 1%. And the lowest tier is ZeroUsed (ZU) with anything lower than 1%.
If a card is on a lower tier, do not feel bad. Just the fact that the card is in a lower tier does not mean that it is bad (unless it is in ZU).
Eventually I might start hosting tournaments that play around these tiers. Any cards that are placed in lower tiers can easily be played in higher tiers. For example, in an UU Tournament you are allowed to use cards that are placed in NU. However you are not allowed to run cards that are placed in OU.
Worship the 9 Titans
(Golem, PEKKA, Lava Hound, Dragon, Giant Skeleton, Scorcher, Super PEKKA, Electro Dragon, Goblin Giant)
Obey the 4 Immortal Armies
(Skeleton Army, Minion Horde, Goblin Gang, Critter Swarm)
Teach the 12 Titan Babies
(Golemite, Mini PEKKA, Baby Dragon, Lava Pup, Sparky, Inferno Dragon, Ice Golem, Balloon, Cannon Cart, Dropship, Flying Machine, Deployable Turret)
Protect the 12 Peasants
(Skeletons, Goblins, Spear Goblins, Minions, Bats, Critters, Fire Spirits, Ice Spirits, Crystal Critters, Critter Bats, Explosive Drones, Beta Minion)
Babysit the Titan Grandchild
Check my AMA here
This is my favorite discussion ever (not created by me): https://communityroyale.com/discussion/1676/how-arena-1-has-mirror-0-max-trophy#latest