Repulse (Invasion/Planeshift/Apocalypse) Cantrips are fun, since you do not have to spend a card to gain an effect - it breaks the card/mana equation of playing a spell
RISHKARS EXPERTISE Hand refills are the other great way to draw in green, and there are plenty of options
Emrakul, the Aeons Torn is a 15-mana flying 15/15 that cant be countered, gives you an extra turn after you cast it, has protection from cards that have colours and has Annihilator 6
While both are interesting to build around, Wakka lets us blend the two strategies - without restricting us to creature type or color identity
I wonder what the version of Price of Betrayal that could target any number of permanents would cost
Its as efficient as they come, with only a one-mana cost, but its ability to save your butt in a game is beyond measure