Sauron, the Dark Lord Sauron, the Dark Lord is a very strong threat on its own
Of course, this lets you control which card ends up in your hand at the most basic level
Any Planeswalker, token maker, creature with +1/+1 counters, artifact with charge counters, and so much more is downright abusive when fighting at the Selesnya Loft Gardens
Etali, Primal Conqueror is a lot of stupid Dinosaur fun, and it's my Commander for Historic Brawl in Arena because it is just so satisfying to cast big spells for free (think the likes of Emrakul, the Promised End)
How do I put my MTG cards into sleeves
You can attack with a Kaalia on turn four or five, and then drop an Akroma, Angel of Wrath or an Ancient Copper Dragon to attack alongside her