I don't have as many "best kept secrets" at KI as I do at WDW, but I'd say probably high on the list is taking the time to relax and feed the fish in Oktoberfest. GatorGirl and I like to do that in between rides and shows. Also, even though it's known to many of us on here but not widepread among the GP, Adventure Express is a great night ride.
Holiday Horror also features "Kinzel for President" signs (or something to that effect) in the President's Day room. I really hope there isn't a hidden meaning to be analyzed from that, either.
Unless, of course, someone actually believes all problems in the world can be solved with trashcans and concrete.