I don’t really know if I can think of any true fails as I would define it. Maybe just the Swiss/Camp Flame is the only true failure that I can think of right now
There are a number of tools I really question the usability of though. They really only marginally work as advertised or they are damaged quite easily when being used for an advertised task. Now is this a fail? I don’t know. I can certainly make just about any tool fail but they are 100% user caused by me. Not a failure related to quality. For example every single time I have ever used the screw driver tip on the can opener to turn a #2 Philips I end up putting a slight tweak in the end of the tool. That’s with me not trying to put much force on it. This isn’t Victorinox’s problem with their quality. There’s a reason why flat bladed screw drivers aren’t marketed as being able to turn a #2 Philips even though they sort of can. But in an emergency yes it will work quite often. So that should be kept in mind when we hear people talk about tool failures.
Product flops or market failures are different to me. I think they are super interesting from a collectors point of view.