I'm really enjoying this thread; my neck is getting sore from nodding. Some more..

Hotel doors that close too aggressively while you're juggling the room key, your carryon, and your checked bag. Why not just have a loop and a hook on the back of the door and adjacent wall?

Not enough room for two toilet kits in the loo; it would be okay even if one uses a hook on the wall.

Seat lights on planes that can't be re-aimed.