Apart from all the standard things like, screws missing, wheel spats falling off, flat spots on tires, loose tail wheel leaf springs, missing inspection covers in fabric wings, or loose ones, stiffs controls, loose cables, weeping fuel drains, cracked spinner, leaking prop (CSU) etc... the most surprising thing I discovered was a broken spark plug on a Rotax 582. Only reason I found it is I have the habit of checking the leads on the plugs and as I wiggled it, it came off in my hand, with half the plug in-side it! And no, I didn't bend it and break it off! Upon inspection it had been cracked for some time...