I love learning new tweaks for WordPress. The more I learn, the more I see how versatile WordPress truly is.
Quick Note on a Best Practice for Tweaks
You should avoid putting your tweaks into the rewrite.php file since you will most likely have to re-edit the file every time there is a WordPress update.
You should add these tweaks into your theme's functions.php file or otherwise make your own custom plugin.
Changing the Author Permalink Base
Let's say you are after something like yourwebsite.com/conqueror/your-nice-name as opposed to the default author permalink base yourwebsite.com/author/your-nice-name.
$wp_rewrite->author_base=“conqueror”; // Change this to whatever you wish
Check out the other useful post, Useful SQL Queries for WordPress.
What else would you like to see here? I may add more useful tweaks for WordPress here in the future.