Figure I might as well start participating in these eventually, heh, I've been following them since a good while before Arghonaut... Can't remember when though.
I'd like to voice my support for Grass/Water or any other combination with Water. There's not much that I can add to what has already been said about this typing (others pretty much covered that), but if we're going for a sun mon, which is admittedly a little dull, I think the best approach is to do something kind of backwards and unique. A Water type that functions best in Sun, poorly in Rain, and hurts its fellow water types. I think figuring out just how to perfect this would be interesting, at the very least.