!bang is the most useful search feature since I'm Feeling Lucky. I submitted this exact feature to Google years ago, and DuckDuckGo's implementation of it caused me to switch search engines.
You can now do /+search, e.g. /slashdot or whatever. Also all the !bang commands now will take you right to the site if you don't follow them with a search, e.g. !a takes you to amazon.