The earth suddenly reverses rotation. Basically the entire surface of the earth is subjected to a massive reversal of force. The tidal waves would wash over most of the land we have everything would be wrenched asunder the crust of the earth would tear spilling magma into barren oceans.
The earth slows down stops then starts spinning again. Gravity would become weaker and weaker one side of the earth would be perpetual night and the other side perpetual day the atmosphere would dissipate into space along with anything loose on the surface which includes all the water we have all life would perish. Slowly, as the earth starts to spin again gravity might pull some of its materials back down but hardly enough to make a difference. The earth would be a barren wasteland.
The earth suddenly stops spinning. Everything on the surface of the earth including all its water and the atmosphere would be violently flung into outer space. All life would perish as our human corpses hurled at extreme speeds through our solar system.