Minify your HTML by removing all the unnecessary characters.
Minify your JS by removing all the unnecessary characters.
Make sure your passwords are good enough.
Get the gravatar.com globally recognized avatar for any email.
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.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Take an IP and try to look for the domain/host associated with it.