Mewtwo

You have no maximum hand size.
When this creature enters the battlefield, reveal
cards from the top of your library until you have revealed 3 instants and/or sorceries. Put those
into your hand and place the rest of the cards revealed this way on the bottom of your library. Shuffle your library. Until end of turn, you may
cast any instants or sorceries from your hand
without paying their mana costs.