Get approximate IP details.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get all possible details about an SSL certificate.
Get all possible details about a domain name.
Ping a website, server or port..
Generate a URL slug for any string input.
Get the gravatar.com globally recognized avatar for any email.
Make sure your passwords are good enough.
Take an IP and try to look for the domain/host associated with it.