My father said he felt stupid for buying a number of HK auto sears back in the day because the taxes were so high.

Now he regrets he didn't buy them by the pallet load.

The first one I personally regret is I passed on a chance to buy a Japanese Type 99 that saw action on Iwo Jima, with solid provenance, for a relative pittance. There have been others, but that one is the one I really kick myself over.