I like
Rain! I also like
Raine, mostly after a character named Moiraine but now I just like it on its own merits too. I know one little girl named Rayne, and I've also met a girl named
Rain. I've never met a guy
Rain. I don't like it on a boy nearly as much as a girl anyway.. I like Rainy as a nickname (or Rainey, etc.)
I think rain has pretty imagery. Sure, rain can be annoying sometimes, but that's a risk with any word name. Like
Summer-- summer is a season, usually seen as good but there are many annoying things about it (like being too hot, etc.) I don't think something like that should keep you from using a name.