well, not really "acheivment" but when i was a togepi and i used metronome, it used selfdestruct ._. i was versus a gym leader and togepi was my second to the last pokemon. the last was an eevee :: even more useless...
In LG, I was passing the Elite 4 again when I realised I had forgotten to take my lv5 togepi out. All my Pokemon fainted except for Togepi and you won't believe my Luck. It used Hydro Pump, Thunder, Blizzard, Fire Blast, splash and Frenzy Plant and the opponents moves always missed. I ended up beating the Champion with the lv5 Togepi, now lv 43.
I was so pleased with it, it evolved and so I decided to vs my friend with it. Togetic was versing a Sableye and so I used metronome. It turned into explosion o.0
I think I once had a Metronome turn into a Metronome, but I can't quite remember
But check this out:I had my Clefable aganst a gengar, and I used Metronome 10 times, and every single move was a Normal move.
How Annoying is that.
I think they shoulf invent a Metroform for Ditto
Randomly turns into a Random Pokemon with random Moves and nature