The second best feature is that you can specify rewrite rules for URLs in results, using regular expressions. The example one is the most important one for me: rewriting reddit.com to old.reddit.com.
Their "collapse listicles" setting is probably one of the best features when trying to search for products, they squeeze all the listicles together in their own list (usually just below the fold). If you want them, they're there, and if you don't, they take up hardly any space.