I caught Cobalion on my first pokeball (which was a premier ball). It was not a critical catch. Also I caught Reshiram later in my one and only premier ball that I had. It had full HP too, so that was a little bit awsome.
Also when I got pokerus from a pokemon in the wild. That's pretty darn lucky, considerng I can't connect to any WIFI stuff, the pokerus encounter rate is 1/3rd of that of shinies, and ultimately you can't see it when a pokemon has got pokerus, so what was the chance that I was going to battle that pokemon - I normally would flee. So the last one was probably something equal to meeting a shiny Beldum and then catch it on the first pokeball without weakening it.