Clothes that you're 100% sure you don't want anymore!
I had two Coach purses which I loved for a few months, but after a while I started to hate them and the brand hehe sorry.
So I donated them, and I REGRET NOTHING!
Also a few years ago I tried to sell about 70% of my closet to Plato's closet, sold most of it, but the stuff they didn't pay me for I just donated.
THAT I regret, I realized that I shouldn't sell my stuff so cheap anymore and get ripped off like at Plato's closet, only got about 20 percent of what I paid for
If you have clothes you don't think you want anymore you should just store it in a box or something then open it a few years later and be maybe be happy because you find yourself liking those clothes/shoes/bags/whatever again.