I've got a three-gallon ball-lock keg in very good shape. I love it... but what I'd love more (but don't want to spend $$ on) is a DudaDiesel plate chiller (or something equivalent). I see the kegs going for what, $70 or $80 used - about the same as a 30-plate chiller, new.
If anyone might be interested, I can post picture. For now, trust me that it's in really nice shape for being used.