When being given my severance documents to read I asked the manager to leave the room (his office) to give me an opportunity to read them properly. The look of confusion, he mumbled something about not being able to leave me in there alone, sensitive data etc. So I told him he could leave the door open and wait outside, which he did.
Turns out they had miscalculated and I then refused to leave until it was confirmed it was sorted out with HR.
I was polite and respectful so there wasn't much they could do if they didn't want to look bad.
I then took them to a tribunal for unfair selection procedures and a few other things and had an additional payout.
On another occasion the company announced layoffs and I was selected, on the day I had gone in planning to hand in my notice, so that was a pleasant experience, I think they were surprised how eager I was to go.