1. Ghost: All you need is an old white sheet, and voila! It's simple, but effective. Cut holes for eyes or get creative and create your own design.

2. Zombie: Rummage through your wardrobe for old, unwanted clothes. Splatter some fake blood and dirt on them and paint your face pale with darkened eyes.

3. Black Cat: Dress in all black. Cut out a pair of ears from cardboard and glue them to a headband. Paint a nose and whiskers on your face.

4. Witch/Wizard: Use a bathrobe as your wizarding robe. Carry a stick for a wand, and top it off with a handmade hat from cardboard.

5. Greek God/Goddess: All you need is a white sheet to wrap around yourself, some fake gold leaf for a crown and gold accessories.

6. Emoji Face: Find an emoji you like, then draw or print it onto a large piece of cardstock. Attach it to a stick to hold up to your face.

7. Classic Mummy: Wrap yourself in toilet paper or white cloth strips, ensuring you leave holes to see and breathe.

8. Tourist: Grab a loud Hawaiian shirt, khaki shorts, a hat, and a map. You can even throw on a fanny pack for added effect.

9. Selfie Queen: Carry a selfie stick, wear a tiara, glam up your makeup and clothing.

10. Vampire: Dress in black, paint your face pale, add some blood at the corners of your mouth and use plastic vampire teeth.

11. Robot: Get a cardboard box that fits your torso, cut holes for your head and arms, and spray paint it silver. Add buttons or switches with paint or colored paper.

12. Cereal Killer: Stick empty mini cereal boxes onto a shirt and make it look like you have stabbed them with plastic knives or spoons.

13. Mime: Dress in black and white, add white face paint and exaggerate your facial features with black eyeliner.

14. Nerd: Throw on some glasses, a white button-up shirt tucked into high-waisted trousers, and add a pocket protector filled with pens.

15. Error 404 Costume Not Found: For a clever, easy idea, grab a white T-shirt and write Error 404: Costume Not Found with a marker.

Remember, creativity and originality matter more than the complexity of the costume!