Take an IP and try to look for the domain/host associated with it.
Get approximate IP details.
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.
Convert kilograms (kg) to pounds (lb) with ease.
Check if the URL is cached or not by Google.
Check if the URL is banned and marked as safe/unsafe by Google.
Get & verify the meta tags of any website.
Make sure your passwords are good enough.