Convert text to binary and the other way for any string input.
Convert text to hexadecimal and the other way for any string input.
Convert text to decimal and the other way for any string input.
Convert text to octal and the other way for any string input.
Make sure your passwords are good enough.
Get & verify the meta tags of any website.
Get the web-host of a given website.
Get details of any file type, such as the mime type or last edit date.
Check if the URL is banned and marked as safe/unsafe by Google.
Check if the URL is cached or not by Google.