Aerodactyl is great fun if you want to win without doing any damage (no, seriously), the promo Mankey makes Primeape a valid counter to Pikachu ex decks, and Im constantly trying to cook up something Darkness-flavoured to deal super effective damage to all those pesky Mewtwo ex decks I see
Azelf, Mesprit, or Uxie
Im not entirely sure how this happens, though
Mogis, God of Slaughter deals damage unless opponents are willing to sacrifice a creature, Fate Unraveler deals damage whenever an opponent draws a card, and Blood Seeker deals damage whenever an opponent plays a creature
After all, trading cards were meant to be played with and even rare cards are no exception when you first receive them as kids
In my experience, the Game Changers that win the most games are the ones that generate persistent card advantage: Rhystic Study, Smothering Tithe, Necropotence