Please note that this is only 100% accurate to Generation VII games.
For Generation III games, ignore Abilities introduced in Generation IV or later and Hidden Abilities.
For Generation IV games, ignore Hidden Abilities.
For Generation V games, ignore Abilities introduced in Generation VI or later.
For Generation VI games, ignore Abilities introduced in Generation VII or later.
In Pokémon Black and White, Blue-StripedBasculin have Reckless as their second standard Ability; however, a Blue-Striped Basculin with Rock Head can be obtained from an in-game trade in White. In Pokémon Black 2 and White 2, wild Blue-Striped Basculin have Rock Head as their second standard Ability, but Blue-Striped Basculin bred in Pokémon Black 2 and White 2 have Reckless as their second standard Ability. In Generation VI, Blue-Striped Basculin have Rock Head as their second standard Ability, and Blue-Striped Basculin with Reckless transferred to Pokémon Bank have their Ability changed to Rock Head.
In the Generation V games, Starly has no Hidden Ability, but a Starly with its Hidden Ability flag set will evolve into Staravia with its Hidden Ability Reckless and can produce Starly with their Hidden Ability flag set when bred. A Starly with its Hidden Ability flag set will have its Ability changed to Reckless when transferred to Pokémon Bank.
The power of moves with recoil damage, such as Take Down, and moves that cause the user to take damage if they fail, such as Jump Kick, goes up! But the damage the Pokémon takes also goes up! It has no effects on some moves, such as Struggle and Final Gambit.
Rhyhorn, Rhydon, Rhyperior, and Hitmonlee are the only Pokémon with Reckless that can use all moves affected by Reckless, as they can use them via Mimic. However, Hitmonlee can only have this combination by learning Mimic from the Move Tutor in Pokémon FireRed, LeafGreen, and Emerald, then gaining Reckless by using an Ability Capsule in Generation VI or VII, or by learning Mimic as a Tyrogue and evolving in a Generation IV or V game (in this case, Hitmonlee has a 50% chance of having Reckless, depending on its personality value).