The Kinesis Advantage keyboard [1]. The height of the keys in each column are different because, well, the length of each of our fingers is different. It’s so naturally comfortable that it goes unnoticed and one’s fingers just fall into the right position. Placing one’s fingers offset left or right is so obviously uncomfortable that it’s basically impossible to have off-by-one typos. There is a lot of subtly well-designed ergonomics to this keyboard (though also some not great bits—looking at you, function row).