Cast iron holdfasts that I bought early on in my woodworking journey. The shaft was undersized, and geometry was bad, so it was almost impossible to get it to hold. One day I was pissed and hit it one so hard while trying to seat it that it broke. A related, subsequent purchase is one that I also regret now, although not at the time. The Veritas Hold Down. It works like a dream as far as holding things down goes, but is almost twice as expensive as the Gramercy Hold Fasts, takes up more storage room, and takes twice as long to use. Does the trick very well, yes, but slow and not a good value. However, at the time I didn't have much choice, given that the only holdfasts on the market were the Veritas and the crappy Asian cast iron jobs. If I were in a situation where I had to work quiet though, the Veritas would be the ticket.
I think I donated or threw away the other cast iron holdfast.