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 all possible details about an SSL certificate.
Get all possible details about a domain name.
Ping a website, server or port..
Get the gravatar.com globally recognized avatar for any email.
Check if the URL is cached or not by Google.
Make sure your passwords are good enough.
Convert kilograms (kg) to pounds (lb) with ease.
Get the web-host of a given website.
Get & verify the meta tags of any website.