Stupid PE File Tricks
If you're an aficionado of all things PE file related, you'll get a kick of this article:
https://www.phreedom.org/solar/code/tinype/
It shows all the wild twists and contortions to make a legal 97 byte Win32 PE file.
I think the smallest Win32 binary I ever created was 1KB, but that was just by playing tricks with the linker and my tinycrt library. I never tooks steps like locating code bytes in unused fields in the PE header.