Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get approximate IP details.
Get all possible details about an SSL certificate.
Get all possible details about a domain name.
Make sure your passwords are good enough.
Get all the HTTP headers that an URL returns for a typical GET request.
Ping a website, server or port..
Validate JSON content and make it looks good.