What are your ideas for intentionally poorly-planned traps?

Currently making a one off "Lich's" lair as a minor encounter in OotA. The catch is that the guy isn't a lich, just a noble with lots of money and low intelligence. He only came back to life because of the corruption of Orcus. As such, he made a "death trap" tomb with terribly designed traps.

The trap I have is in the room that holds his "Fylacterey", hidden behind a secret door marked with a giant red S. A three foot tall pedestal in the middle of the room hold what he thinks is his phylactery, and once the box is removed, the door locks and the ceiling starts to lower. However, it's not built to accommodate the pedestal, so when the trap hits it, the ceiling grinds against its internal mechanisms and breaks, leaving a convenient three feet of space.

What are some other "traps" I could include?