[andolanra]

My Firefox install has seven search engines by default in the "one-click search engine" options. By contrast, DuckDuckGo has 13000 bang shortcuts. Sure, you don't need all of them, but I use dozens: some of them almost daily (like !w for Wikipedia and !wt for Wiktionary), some sporadically (like !tw for Twitter or !a for Amazon) and some of them only rarely (e.g. I picked up a Pokémon game recently and consequently have used !bulba to quickly search Bulbapedia, a Pokémon fan wiki.) Of course I can add all those to Firefox, but DuckDuckGo already has them set up, and has many more that I can use without thinking about them. I think that still counts as a killer feature.

[choathedolls]

Firefox is a little lacking in that department. Chromium based browsers on the other hand, anytime a search is used on a page, that gets added to the list in your browser's options.

For example, just used HN's search bar, and there it showed up in the options ready to customise keywords to my liking (if I wanted to change it).

Before anybody claims it's an additional step, it's not. DDG requires you to know what the keyword is before you use it, which is the same as having to use the search on the site before. So I guess I agree it's a killer feature if you exclusively use Firefox for the time being.

[ma2rten]

In chrome you also just start typing the name of the site, until it autocompletes and then hit tab.

For example if I want to want search wikipedia, I type "en.w" and hit tab.