I remember kakashi doing a rasengan effortlessly but he said that doing the rasengan along with adding "an" elemental affinity was extremely difficult. So there COULD in theory be 4 other forms of the completed rasengan. Flame, water, lightening, and earth rasengans would probably be really cool.

Anyways I think the zombie battles will be pretty great. I can't wait to see salamander fight. I could care less about the previous hokage and the fallen akatsuki.