There are quite a few rats with effects that focus on rat swarms and give you advantages when you have more rats in play or allow you to have any number of the same card in your deck
Even if you do wind up losing, this spell is sure to create a lot of memorable moments
Which means that by deck-building standards, you can have, instead of the regular limit of four Llanowar Elves, functionally eight of them with four Llanowars and four Fyndhorns
Spend this mana only to cast a Knight or Equipment spell
Volo is all about anti-Tribal, meaning decks using him will really come alive when using creatures with weird and rare types
Phytotitan At this point I dont think I need to explain why a mono-green, six mana, 7/2 creature that returns to the battlefield from the graveyard is amazing