Creative Last Minute Halloween Costume Ideas

Flower Child or Hippie
Most of us have some clothing, accessories, and shoes we can combine to create a rather authentic hippie looks. A few necklaces, flowy clothing, and a 70s style hat should do the trick.
Zombie
The key to a great zombie is the makeup. Check YouTube for some makeup tutorials for the zombie look. The clothing can be almost anything as long as they look ragged and dirty. This makes it an easy last-minute costume. You can be anything from a zombie cheerleader to a doctor.
Olympic Winner
If you can find an old medal to hang around your neck, you have already gotten a head start. If not, you can easily make one with basic supplies from a local craft store. Then choose clothing for the Olympic event of your choice. You can be a runner, gymnast, tennis player, or whatever sport you love the most.
Chef or Line Cook
Most people have easy access to an apron and basic cooking supplies (maybe even a hairnet for good measure). You can elevate your look with an authentic chef coat and black pants. Chef jackets are readily available at Walmart, Amazon, and other major retailers.
Teacher or Professor
A pair of glasses, studious clothing, a briefcase, and red grading pen should do the trick. You can even get more props from the dollar store or thrift store that are subject specific.