The ones I think are the best are shiny quilava and typhlosion. Not only because they're two of my favorite pokemon, but because I think the dark red suits them extremely well. Unlike some pokemon, it didn't seem like they just chose colors at random (seriously, some shiny color schemes just make me want to cringe).
Then there's shiny dragonair...which, with its complementary colors, seems pretty neat as well. I think that one's also a pretty good one.