1 Imposter Mech
3 Black Widow, Deadly Hunter Black Widow, Double Agent Blacklance Paragon Blight Titan Blightwing Bandit Bloodthirsty Conqueror Blooming Stinger Body Launderer Boggart Cursecrafter Bone Picker Bone-Cairn Butcher Bonepicker Skirge Boot Nipper Burrog Banemaker Bushmaster, Coiled Henchman Cackling Culprit Cackling Slasher Cairn Wanderer Canyon Crawler Carnival Carnivore Cecil, Dark Knight Chevill, Bane of Monsters Cloak and Dagger, Entwined
Grove of the Guardian I remember Grove of the Guardian turning the wheels in my head as a new Magic player, especially since it released alongside the populate mechanic from Return to Ravnica
With cards like [c]Heritage Druid[/c], [c]Nettle Sentinel[/c], and [c]Priest of Titania[/c], you can generate loads of mana in a single turn, drawing cards after every creature you play thanks to Glimpse of Nature, and then playing the cards you draw as well
They can cast that person's spell with any color of mana