My first shiny I ever encountered was a Spinda on Emerald. I wasn't really aware of shinies but a few days later, I realized that I encountered a green Spinda. Checking Serebii if it was right, and yeah..
I felt miserable.
But, a few months ago, I restarted Emerald and encountered a shiny Claydol at Sky Pillar. I was damn happy, cause I could finally capture a shiny in Gen.III (I think it was my first one).