If your opponent discards a card while you control Leyline of the Void, abilities that check whether a card is discarded (such as Hollow One, or a madness ability of the discarded card) still work, even though that card never reaches that player's graveyard
Examples in this category are Additionally, you'll also see some references to the Game Changers list
Other than the art of the borderless version being weirdly washed out, the text of the card reads Return Llanowar Greenwidow from your graveyard to the battlefield tapped, tapped. Thats too many taps
In addition, the ability to create tokens and boost all of your friends has me smiling
You've also got ninjutsu, which lets you swap an unblocked creature with a ninja for a cost, and can be a lot of fun to play with, but mostly in casual formats