CSS frameworks that are smart enough to only apply CSS that your site actually uses. And no, I have zero interest in compiling my own version of Bootstrap to achieve this.<p>A static generator in PHP that just works with shared hosting without the need for any 3rd party libraries or frameworks. Just upload, unzip and you are set.<p>Basic persistent key-value data storage in the browser using only HTML.
Drag and drop application building like .net Winforms.<p>The productivity boost of quickly making forms and only coding the button actions is unmatched. No "RAD" web framework on the web is anything near that.