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..
Extract email addresses from any kind of text content.
Convert markdown snippets to raw HTML code.
Convert forum type bbcode snippets to raw HTML code.
Get all the HTTP headers that an URL returns for a typical GET request.
Validate JSON content and make it looks good.