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.
Generate passwords with custom length and custom settings.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Check if the URL is cached or not by Google.
Make sure your passwords are good enough.
Take an IP and try to look for the domain/host associated with it.
Get approximate IP details.