I vote for:
1)
Metamorphosis, because it has a nice, unique, non-broken effect of changing your Mark into something else.
2)
Fly, because I am amazed how Air has yet to get a card which can make a creature Airborne and able to use Dive.
3)
Healing pod, because it makes sense Life to have a card which drains all green quanta to remove all poison.
4)
Upgrade/Downgrade, since it is fun and not broken.