Minify your HTML by removing all the unnecessary characters.
Minify your CSS by removing all the unnecessary characters.
Easily convert IDN to Punnycode and back.
Extract email addresses from any kind of text content.
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.
Make sure your passwords are good enough.
Get all possible details about an SSL certificate.