Take an IP and try to look for the domain/host associated with it.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get approximate IP details.
Get all possible details about an SSL certificate.
Ping a website, server or port..
Convert text to binary and the other way for any string input.
Minify your HTML by removing all the unnecessary characters.
Minify your JS by removing all the unnecessary characters.
Encode any string input to Base64.
Minify your CSS by removing all the unnecessary characters.
Make sure your passwords are good enough.