Hmmm, I'm going with Ocean again?
Pros: it sustains life for all sea animals yet is dangerous enough to take life (this is a powerful & beautiful thing), it's filled with beautiful creatures, it reflects the blue sky, fun for swimming, sailing, traveling.
Cons: it tastes gross, you can die if you're caught in a tidal wave, storm or attacked by one of its creatures, it makes tsunamis possible (my ultimate fear in life).
Rainbow Brite