So I've had 2 shinies in my life. I've never MM'd or used the Pokeradar, it was just by chance. The 1st was a Blood red Duskull in Ruby on my first playthrough. The 2nd was when I was using an action replay to get pokemon I want, but the codes I had at the time didn't allow me to use the shiny code in tandem with the wild pokemon modifier. So I was catching my team when I got to Gengar and wouldn't you know it, he popped up shiny.

Also shiny general.