If Jenova dies at the same time as one or more Mutants you control, its last ability will trigger for each of those Mutants (including itself if it somehow became a mutant)
Oko is another way to beef up [Card]Ornithopter[/Card], an excellent card to cast off [Card]Springleaf Drum[/Card] turn two and a format staple on-rate so it slots in nicely here
If you can hardcast it and your deck is capable of holding off Burn and Abzan decks on its own, you'll find this very powerful whether it's in the opener or not
You get to trigger its explosively recursive ability whenever it mutates, and you can use cards like Buried Alive or Final Parting to tutor creatures into your graveyard that later can enter the battlefield for free
As long as its a plant, its fair game, allowing you to get big beatsticks like Gigaplant out on the field without even having to Normal summon them
Imduk the World Chalice Dragon currently starts at 8.37