I had an external HD on my A1200. For some reason I've always had trouble with it disconnecting and I once made the mistake of connecting it backwards (it was a special connector that had power and IDE lines in one). Long story short, I killed the main harddrive. A friend of mine who had stored some art he was creating on Deluxe Paint on my system was pissed.

Oh, and for some reason everytime I had to open my A3000, it drew blood.