Minify your HTML by removing all the unnecessary characters.
Minify your JS by removing all the unnecessary characters.
Extract email addresses from any kind of text content.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get approximate IP details.
Get all possible details about a domain name.
Take an IP and try to look for the domain/host associated with it.
Convert a number to written, spelled out words.