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.
Compress and optimize images for a smaller image size but still high quality.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Extract email addresses from any kind of text content.
Take an IP and try to look for the domain/host associated with it.
Get approximate IP details.
Make sure your passwords are good enough.