Some very interesting challenges. I particularly like number 4. I love "traps" like that. It also made me think of one from the L5R module Tomb of Iuchiban. It was this room with the infamous closing walls trap. The closing walls had a single niche in each of them that one person could fit in. Once the walls were five feet apart they just stopped and moved back and so were no danger at all. The idea was it makes "less honourable" PCs murder each other as they fight over who gets to go into a niche.