I remember about 4 years ago I was walking through route 210 (north) on my Diamond version, I hadn't used Defog to clear out the fog. As I was going to press X to open the menu, I hit Y instead, my Pokeradar was registered so it activated. I could barely see the grass patches in the fog, I just walked around and by chance ran into a shiny Machop! (Which I caught) ... It's long gone now though since I traded that game in a while ago.
However, literally just 10 minutes ago I encountered a shiny Wooper in Pokemon Diamond (I purchased it and all the NDS Pokemon games to play through recently), I was in the Marsh looking for Croagunk, I encountered it like 6 times and it still escaped! ... Then a shiny Wooper appears, I chose to throw the ball straight away (who wouldn't?!) It didn't shake once, broke free. *Heart skipped a beat*... It chose to stay and watch carefully though haha! *Sigh of relief* ... Threw my next Safari Ball which eventually caught it! :D