ITT: Pokemon that were, in one game or another, WAY too fucking hard to find for how good they are.

I was thinking about ORAS and this little fucker flashed into my mind. A TWO FUCKING PERCENT encounter rate in the foggy area of Mt. Pyre. It literally took me longer to find one of these than to find Feebas, and it's total shit.

Any other 'Mons that have required way too much effort for what you get out of finding them?