The last thing I bought then felt regret buying it, is 1/4 kilo of coffee beans I liked it's smell in the shop, then found it very bad quality ( I trusted my nose)

Any item that could break shortly or doesn't function efficiently on the long run with a shorter than expected life span.It makes me feel sorry for the money I paid for it ,specially if it was quite expensive and or I have been told that it is a quality product.

A good question. I bought a pair of shoes that felt great in the shop, but after wearing them to a wedding, I ended up with blistered feet.

Domain names for opening web sites, but it took to much work for it, I let them regretfully expire.