Incessant bothering while you're wandering around. It makes me leave the store empty-handed.
Up-selling at the till. One store here is so bad for it, that if I had more balls I'd just say upfront, before they even launch in, that I'm only interested in what I, personally, have brought up to the till, and no, I don't need a water bottle, reusable shopping bag, to make a donation to xxx charity / your bottom line.
To sign up to your loyalty programme.
To engage in meaningless chat about how my day's going, and what my plans are for the remainder of it. It's completely insincere, and you don't give a shit. There are better ways of pleasantly passing our 90 seconds together than by asking me inane shit about my day.
I know these directives come from on high, and that it's the poor minions who have to carry it all out, but that makes it even worse.
The people actually forced to endure it - sales people and customers - hate it!