You can use the Terminal to list files and folders, restrict the lists to only large files and folders, and also just show the ones that use the most space.
If you need to create a random password outside of Safari or another password manager, you can use a variety of techniques. You can use the Keychain Access app, some Terminal commands, or even make your own Automator action to generate one on demand.
You can go to the Terminal and use simple one-line shell scripts to get various pieces of information such as the date and time, your Internet IP address and your Wi-Fi network name. Using Automator, you can incorporate these bits of information into a simple notification that appears whenever you press a keyboard shortcut.