Duh, I'm an idiot. Mentioned STABbed Ice Beams while forgetting that Rayquaza gets a similar bonus from Dragon moves. Stupid me. Thanks for adding your input to cover up my deficiencies, H Man. ^_^

In any event, there are a number of things you could do with Rayquaza. I like to cover many different types, while some prefer to specialize in particular strategies. Lots of movesets will work, especially considering Rayquaza's natural strength. Since it's banned in most tournaments, and many casual battlers consider legendaries fairly cheap, you may as well just use it however you prefer for in-game play.