Funny/awesome story. It was Rayquaza. I was playing the OG Sapphire and reaaaallly wanted a black sky dragon, so I just kept soft resetting. I told myself I wouldn't try forever and would probably stop at around 2000. I got it on about 350. I was ecstatic.
A Minun in Sapphire, via random encounter. Was pretty shocked when it appeared on screen. Sadly he is long gone now.