I'm another Kagi fan - after customising it a little it's just so good, and I haven't even played with features like lenses.
I really like the custom bang searches (e.g. I could make !ks gravity
search on simple Wikipedia), especially on mobile since Firefox Android doesn't support the normal browser quicksearches (where you set a keyword for each search).
It's been mentioned in every episode so far, but mostly the contestants are ignoring it.