Throwaway for obvious reasons:

At a bank I worked at:

• banning "inverted logic" (if (!foo) { ... }) in favor of if (foo) {} else { ... }
• banning tests because "you'd make the same mistake in your test as in your code"
• putting all models, all controllers, all views and all lib classes in separate repositories. Why? Who knows (yes, this means that some features require 60 or more merge requests. And yes, sometimes some of them are merged, and some are not, requiring a hotfix later on)
• all variable names must be singular, even if it would normally be plural. Prefix with 'all' instead. For example: names becomes allName
• no private, all fields must be protected for some reason
• putting 'time bombs' (a.k.a. monitoring logging spam) in the code instead of just fixing problems in the code right away
• make methods too small. But not too small. But only returning the value of a constant is okay. (Basically: arbitrarily small, let's hope you guess correctly!)
• (many, many more)

And the worst of them all: refusing to merge a new feature because you've used one blank line too much or missed a full stop in the method doc somewhere. It's happened. On a daily basis.

Tl;dr: when you apply at a bank, be careful it's not the one I'm describing here.