Moxie
Raises Attack one stage upon KOing a Pokémon.
Full effect
This Pokémon's Attack rises one stage upon knocking out another Pokémon, even a friendly Pokémon. This ability does not take effect when the Pokémon indirectly causes another Pokémon to faint, e.g. through poison or Spikes. If this Pokémon knocks out a Pokémon with Mummy, the former's ability will change without taking effect.
In game description
When the Pokémon knocks out a target, it shows moxie, which boosts its Attack stat.
Pokemon with Moxie
Pinsir
hidden
#0130
Gyarados
hidden
#0214
Heracross
hidden
#0262
Mightyena
hidden
#0373
Salamence
hidden
#0430
Honchkrow
hidden
#0551
Sandile
#0552
Krokorok
#0553
Krookodile
#0559
Scraggy
#0560
Scrafty
#0667
Litleo
hidden
#0668
Pyroar Male
hidden
#0912
Quaxly
hidden
#0913
Quaxwell
hidden
#0914
Quaquaval
hidden
Using Moxie in Cobblemon
Abilities are passive and always active, so Moxie costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.