You'll be surprised...
Everyone will be burnt because oxygen helps protect us from the harmful UV Rays; there would be no beach to get burnt at, (the ocean will evaporate into space!)
The earth's crust would crumble because the earth's crust is 45% oxygen. Buildings made from concrete will turn into dust - oxygen is an important binder in concrete. Did I mention everyone's inner ear will pop because air pressure is 21% oxygen? Still not convinced that we need oxygen?
The daytime sky would almost turn black because of the fewer particles to bounce light back. Water is 1/3 oxygen so it would turn into a gas and expand in volume. Now we're almost there.
All untreated metal will spot weld to each other. Why? Because the only thing that is stopping metal from welding to each other is a layer of oxidation. So that sums it up and if you still think it's not that bad here's one more fact, every living cell would explode into hydrogen gas!
Well, I hope you enjoyed this article, though I must give full credit to this Buzzed video for the facts!