1.68. A man is found hanging in a locked room with a puddle of water under his feet. (This is different from #1.67.)
1.68 answer: He stood on a block of ice (or a mound of snow) to hang himself. The fact that there's no furniture in the room can be added to the statement, but if it's mentioned in conjunction with the puddle of water the answer tends to be guessed more easily.
1.68a. Same without the puddle of water.
1.68a answer: It was dry ice instead of water ice. (From Stories With Holes.)