We can't forget about the Spellcasters' Deck when it was the deck that started the game. Of all the cards Yugi/The Pharaoh used, his favorite and most famous card is the Dark Magician. Also, the Dark Magician Girl, of course, and Dark Magician of Chaos no less. Yeah, there's plenty of support cards that aid spellcasters too and so much more. Countless variety decks and opportunities for different strategies to overpower others to make surprising outcomes in duels.
More of my favorite spellcasters:
(The MOST powerful spellcaster to appear in Yu-Gi-Oh! the Movie is none other than the "Sorcerer of Dark Magic"with 3200 ATK points, 2800 DEF points, and the monster effect of negating/destroying trap cards by choice. In the movie, however, it appears it can increase its attack points by the number of spellcasters in the Graveyard.)
Magicians of Bonds and Unity