Rayquaza, along with being my favorite Pokémon in general. It just has this appearance that just suggests... well, everything to you. It has a menacing, mystic look, and the colour palette it has adds a lot to its design. It also has a great selection of moves to choose from, and no other legendary can beat it in terms of nearly everything (apart from stats/moves, but that's a different story).
So, yes, definitely Rayquaza.