Back in college, a friend of mine had just come from a Job Fair at the end of October to a bit of a get-together with costumes. He bet me that he couldn't come up with a working costume right then and there, and I - like a sucker - fell for it. You see, he was in black with a white collared shirt and black tie. All he did was put a long piece of tape on his tie and...voila!
War Boy outfit from Mad Max: Fury Road. Some white body paint and a cheap swimming cap. Don't know if you'd be able to find chrome-coloured food spray on such a short notice though. Party supply store or a craft store might have some. My local supermarkets never carry chrome coloured food spray but other places might. Some black paint for the forehead might be useful as well. Add to that some black pants and a couple of cheap belts, cheap black gloves couldn't hurt and voila, you've got a war boy. Cheap, easy and the only time it'll relevant. Not sure how to pull off the dry mouth look. Maybe sucking on some red candy to make your mouth all red inside.
Superman is easy as hell and thats what I'm doing this year while I hand out candy. Gotta have a red tie for that in addition to the oxford and the Superman t-shirt. It just isn't complete without the tie, not imo anyways.