Minify your HTML by removing all the unnecessary characters.
Minify your CSS by removing all the unnecessary characters.
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.
Take an IP and try to look for the domain/host associated with it.
Get all the HTTP headers that an URL returns for a typical GET request.
Validate JSON content and make it looks good.