Wildcards are special since they allow you to bend the rules of the Pick 10 system. You can, for example, open up additional slots for weapons, equipment and perks.
There are three Wildcard slots that can be filled, with each slot costing one point towards your build. Some Wildcards, like the Perk Greed's, require you to invest additional points to the item occupying the newly opened slot.
Perk 1 Greed
Allows a second Perk 1 to be taken.
Unlocked at Rank 7
Perk 2 Greed
Allows a second Perk 2 to be taken.
Unlocked at Rank 10
Perk 3 Greed
Allows a second Perk 3 to be taken.
Unlocked at Rank 13
Primary Gunfighter 1
Unlocks one additional attachment slot for your primary weapon.
Unlocked at Rank 16
Overkill
Allows you to take a primary weapon in your secondary weapon slot. This is only useful if you utilize it correctly, i.e., have a medium- to long-range weapon paired with a close-quarters weapon.
Unlocked at Rank 19
Secondary Gunfighter
Unlocks one additional attachment slot on your secondary weapon.
Unlocked at Rank 22
Tactician
Replaces your Lethal slot with a second Tactician slot.
Unlocked at Rank 25
Primary Gunfighter 2
Unlocks one additional attachment slot for your primary weapon.
Unlocked at Rank 28
Danger Close
Take a second lethal equipment with you.
Unlocked at Rank 31
Primary Gunfighter 3
Unlocks one additional attachment slot for your primary weapon.
Unlocked at Rank 34