Giovanni's Machoke (MODG2 42)
Flip a coin. If tails, this attack does no damage to the Defending Pokémon and Giovanni's Machoke does 100 damage to itself.
Flip a coin. If heads, this attack does 20 damage plus 20 more damage and the Defending Pokémon is now Paralyzed. If tails, this attack does 20 damage.