Soluciones:

1 He is in an airplane. The motor quits, he crashes and dies.
2 The man is a midget, he can't reach the button for the 24th floor!
3 He stood on a big cube of ice. It melted.
4 The man had the hiccups. The bartender used the gun to scare the man, thus curing his hiccups.
5 He was a skydiver, and his parachute didn't open.
6 He pulled the plug on the drain in the tub.
7 He is in a hospital, and his wife is a patient. She lives only by a life-support system. The power went out, thus the life-support system went off.
8 The two bodies in the ice did not have bellybuttons.
9 He is in the cabin of a plane. The plane crashed and he died.
10 Gertrude and Zelda are fish. The fish tank fell and broke on the floor, thus killing the two fish.
11 The ice in both drinks was laced with poison. The ice had a chance to melt in the glass of the twin who drank it slowly.
12 They are playing baseball. The man in the mask is the Referee, and the girl is on third plate.