Self-service checkouts.
How have they still not figured this gooseberry fool out? Tesco used to have the best system by a mile (i.e. one that actually worked and wasn't hyper-sensitive) but they've recently changed the software and oh of course, it's a load of gooseberry fool now.
When you first come to use it you have two options: 'start' or 'use your own bags'. So I select the using my own bag option and put the bags in the bagging area. Then when you select the option to start scanning your items, UNEXPECTED ITEM IN BAGGING AREA. For strawberry float sake, you literally just told me to put my bags in the bagging area, it shouldn't be unexpected at all.
So you pick the bags up to stop the whining voice (about the bags I've just put down which it told me to put down), and - while still holding your bags with one hand - you can now start scanning your items with your other hand. So you scan the first item and put both the bags and the item down, and it starts saying ASSISTANCE NEEDED, with a pop-up giving two more options: store login, or using own bag. So you select using own bag, and finally you can get on with scanning things. How many strawberry floating times do I have to tell you that I'm using my own bag? What's the point of having that as one of the options when you start using the machine, if on two separate occasions it forgets or ignores it?
Also annoying is when you have some fruit or veg to put through and you need to weigh it, so you have to tap the 'look up item' button. The annoying voice then says "look up your favourite item, or have a browse". What? I'm not doing either of those things. I just want to look up the item I'm currently putting through the checkout. I don't know what my 'favourite item' has got to do with anything, and why would I want to 'have a browse', when I'm clearly only looking for one specific item.
Do the people who design these things even test them out? Why Tesco have changed it when it worked before is baffling.