Last week I bought one of those giant vacuum insulated travel mugs (not a Stanley) from a discount variety store, along with a bunch of other things. After I paid, the cashier asked "do you want the receipt?", I normally say no, but this time for some reason I said yes. After I left the store, my kids needed to use the restroom, so while they went I sat down on the bench and absently looked through the receipt in my hand. I immediately noticed I got charged twice for the mug. The cashier must've double scanned it. I went back to the store, showed a manager my receipt, and they refunded me the difference.

That was technically my last refund, but the last product I actually returned was a set of tws (true-wireless-stereo) IEMs (fancy earbuds). They were a brand new model just released with great reviews, I bought them from Amazon, received them, and used them about a week. During that week I noticed every time they were in my ears, my ear canals got super irritated and my ears felt warm. And whenever I removed them the insides of my ears would be crazy itchy for hours afterwards. It got to a point after a week of use that my ear canals would swell and close up about 15 minutes after I put the earbuds in my ears. Didn't take a rocket surgeon to work out I was allergic to whatever material that earphone was made of. I still had the box and all the packaging, submitted a return to Amazon with the comment "my ears are allergic to those earphones" and they accepted it no problems, I got a full refund.