I disabled all magic in the address bar so if I type "foo" it tries to connect to "http://foo" or else returns an "Unable to Connect" error. I was surprised how many steps were required to accomplish this.
I'd love to read the details on what you did, and I'm pretty sure plenty of others here would, too.
Set keyword.enabled to false in about:config. I do this because if I want to search, I can just press Ctrl+K or click on the search bar. I use Ctrl+L or click on the location bar only when I want to navigate to a specific URL.