Here are some file kinds / types that I like, and ones I have some dirt on.
Was always intrigued by these files. Used for describing contents of archive sand folders.
Google Chrome extensions. The 'shop' doesn't let you just download them, so the only working solution I found was using the Chrome Extension Downloader website to grab them.
File for standardising preferences across text editors, things such as tab length, character format. Also handy for formatting on Github ;)
see §.gitignore in the page for Git.