My first seen and first caught was a Zubat in Leaf Green. I looked it up online (I'd never even caught a Zubat before) and found out that, if it was happy enough, it evolved into this thing called Crobat that had good stats and could learn Fly, so I kept it in my party. I didn't like Golbat much (and still don't) so I was just looking forward to it evolving that much more.
I bet I watched that Golbat start to evolve, then stop, half a dozen times. I tried everything I could think of, but it just wouldn't evolve. I finally gave up and put it in a box.
It wasn't until after I beat the E4 and got the National Dex, and figured out that that meant that a whole bunch of pokemon that hadn't been available before were now, that I had some idea of what the problem was. So I got the Golbat out of the PC and gave it a Rare Candy, and presto - a shiny Crobat. Finally. I used it from then on and was very impressed, and have gone out of my way to catch a good Zubat and evolve it into a Crobat in every game they've been in since.
That particular one currently lives in my Emerald, along with all my other 3rd gen shinies. And I actually caught another shiny Zubat in Diamond, but even though it's got awesome stats, I haven't used it, just because I really prefer shiny Zubat over shiny Crobat.