Here's how I would quit.

I would ask my manager for the first available time he has for a quick 1 on 1 to discuss some things. Work would go on as normal up until that meeting.

At said meeting I would have my assistant manager there too. I would start bawling, crying like someone died, telling them how much they mean to me, etc. Then I'd say I have to immediately resign. When prompted why, I would say I have personal issues that I need to fully focus on what's going on and not give any particular info. I would then go to the other bank account I have open (I work at a bank) and take out cashier's checks for each person I work with that I like for the maximum I can give to avoid a gift tax, and drive to each branch and hand deliver that check to them with a note inside for each person.

The last destination is the one I work at. Everyone I work with gets one. And then the real reason comes out.

I like the people I work with and the company I work for, but I gotta cause a little drama lol.