I have had this experience with a custom knife at a show. I don't remember what maker the knife was. some thing "uber stealth" lots of pointy bits and things on the blade to catch and hang up (think Dark ops only a little less over the top, but higher priced custom). I picked one up and for a second thought I got a finger full of blade, then I realized that the scales were not flush on the handle, the area where there was a finger notch was almost razor sharp, and way past the edge of the front of the metal of the tang. I checked several more of the knives and all had this uncomfortable overlap with sharp scales. (all the while the seller dressed in full battle fatigues and boots, patches all over the place etc) is spouting that they are the worlds best, high speed yadda yadda. I did not say anything (his attitude almost knocked me over from across the room).
Another similar situation, I was looking at a gun shop at a used 1911 Colt. It was a very beautiful gun, and the fit and wear looked like new. I noticed that the hammer would fall even when you weren't even touching the grip safety. The gun also had the lightest trigger I have ever felt in my whole life, including dedicated target .22's etc. While looking at it, with the hammer back I was not touching either the trigger or the grip safety and a slight shift in my hand dropped the hammer. (I thought I must have touched something, and I always check to see if I can lower the hammer with the trigger, but without depressing the grip safety, some thing dangerous I always check when looking at a used 1911, you never know what some "gun expert, weekend warrior" did to it, what with all the drop in parts available etc). I waited till no other customers were there and told the store owner. He basically told me he did not care how dangerous it was, it was used and sold as is, buy at your own risk, why would I put any money into it just to make it safe, guns are inherently dangerous (even thought the shop had a full time gunsmith). He put it back up on the used sale wall. I vowed to never buy anything from that shop. I shudder to think of some schmo carrying that thing locked and cocked and blowing a hole in his but.