Leaving a job mainly because of a new manager who was making changes for changes sake and as a result Fucking everything up as she clearly didn't understand how our shop worked and was pissing off customers and staff alike. Takings massively down, I was the 4th staff member to quit within about 6 weeks, chain but corner shop type place. I had a new job in admin management which was more my speed (I'd been doing the shop job part time as was recovering from a bout of illness that had knocked me sideways it was a stopgap for me but not for the others that had quit). Just so happened the day I was handing in my official notice regional management were visiting (I suspect due to concerns over reduced takings etc)
I was much younger and less confident then, and almost hesitated to hand it in but I had to in order to be able to start the new job on time.
So I hand the letter in...which she had been expecting, but then she tried to make herself look good in front of the regional bods when I did
"Well graphista is on to bigger and better things now, after being just a short while under my leadership"
Which was bollocks!
I felt brave seeing I was leaving anyway and didn't need a reference.
So I calmly replied
"You and I both know EXACTLY why I am leaving and yes it's because of you but not in the way you're making out! Just as it was because of you (named other colleagues - one of whom had been there over 20 years) left and just as customers are leaving in their droves"
I then turned to the regional managers and said simply
"Lovely to meet you - and good luck hiring and keeping staff here I think you'll need it"
Now I'm absolutely of course certain that the regional people were very much already aware of the problems she was causing, but she was gone before I finished my notice and the company tried to get me to stay, but I'd had enough by that point and I was ready for the new job.
The funny part was my nickname at that job was "mouse" as in quiet as a. Unbeknown to me a colleague overheard and shared with others and was apparently completely gobsmacked I even had that in me! 
My gran was once telling us of dads birth and said he wouldn't breathe and so they smacked his bum to startle him into doing so, quick as a flash my sister said "so that's why his face always looks like his arse has just been skelped!"
@Amdone123 yours reminds me of another shop one. I once worked in a shop in a town STUFFED With genuine world famous celebs. So me and the rest of the staff were pretty nonchalant about it all as were the rest of the town. One time a not actually very famous actress (not even in uk) came in, she'd not had a lead role ever and the role she was most famous for was about 15 years before this incident, yet she came in one day, tried to queue jump and then actually uttered the words "don't you know who I am?" My manager and I were in the back room having lunch but the layout inc a mirror meant we could see and hear customers but they couldn't see us. Our 17 year old colleague honestly and innocently answered "err no actually, and you need to go to the back of the queue madam" manager and I (we did know who she was mainly as she was at the time married to someone very famous) silent corpsed, she went all blustery and red and stormed out "I have a lot of money to spend and you've lost my custom!"
Colleague then continues to serve, 1st person says "you don't need customers like that anyway" to which the 2nd customer politely agrees. 2nd customer? Ringo Starr!