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 a domain name.
Ping a website, server or port..
Get all possible details about an SSL certificate.
Make sure your passwords are good enough.
Extract email addresses from any kind of text content.
Use the Google translator API to generate text to speech audio.