When I was a kid, the first shiny I ever encountered was a shiny spinda. For the past... 10 years, I thought it was the dumbest/ most worthless shiny to find, but then I realized there's like 2 million unique patterns spinda can have, so a shiny spinda is actually the most valuable/rarest shiny, because there's probably no other like it.
In XY, I was ev training my Gardevoir on route 12?, and I kept getting the rare hoard (4 tauros 1 miltank,) and I thought to myself "You know what? I'm going to encounter a shiny miltank and have to defeat all the tauros and it's going to screw up my ev training." The very next hoard, that's EXACTLY what happened.
The most recent shiny I found was a shiny smeargle on route 7. I was actually trying to hatch my friend a shiny gastly, and since my d-pad is worn out I use the stick, and I accidentally went off course into the grass and bam, TIMID shiny smeargle. Since it only knows sketch, it was one move away from KOing itself when I caught it.
I have hunted the hell out of route 7, so far I've caught a shiny hoppip, croagunk, ducklett, psyduck, and that smeargle, but the shiny I want the most is Roselia.
I caught my croagunk when I was just practicing chaining, when I'd get a pokemon I didn't want, I'd soft reset. So I didn't really want a croagunk, but I defeated it anyway on the first bush instead of resetting. Second chain: shiny.
Today was the day, I was finally going to get my roselia. I was chaining, the whole time i kept telling myself "you're going to break your chain, its only a matter of time, so don't get your hopes up." I followed all of the rules, and finally got to a chain of 39, the highest chain I've reached. This is when I told myself "YOU'VE GOT THIS IN THE BAG! JUST ONE MORE PATCH!" at the same time, I was very calm and didn't get reckless. So I picked the perfect patch-- 4 spaces away, not on an edge, not by other patches, right speed. And guess who was there? Smeargle. I like to think this was a foreshadow for the random shiny smeargle I got. I was really upset. Moreso, I ended up getting the shiny hoppip and psyduck from hoard hunting for roselia. Now I'm masuda methoding, and this is one of the longest hunts I've had.
Last one: I was breeding for a perfect eevee with anticipation; didn't have to be female or shiny. Just anticipation/ perfect. Well after 15 eggs I got a shiny female 5IV'd but not HA. I was just thinking how po'd everyone who wants a shiny eevee would be. I named her Elsa and evolved her into my favorite eeveelution: glaceon (since the HA and regular ability weren't much different)