A couple of years ago, I've found a gem of a bike. It looked maybe 15-20 years old and was clearly heavily used - frame was full of scratches and such. The color scheme was pretty ugly and was just a tad too small for an adult. But I noticed that all the components were actually decent - mostly Shimano XT, obviously very old models. After servicing it, it rode very well and I didn't have to worry about thiefs since it was pretty cheap and even more cheap looking. I still locked it, but the peace of mind was nice.