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.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get all possible details about a domain name.
Extract email addresses from any kind of text content.
Take an IP and try to look for the domain/host associated with it.
Get all possible details about an SSL certificate.
Make sure your passwords are good enough.