Answer:
depends on your grade
Explanation:
1.if u are a junior grader then a periscope will be great
2.for middle graders try making a vacuum cleaner with a plastic bottle
3.for high schoolers try something good and unique like a remote control car or u can also make one sonar just (a distance calculator of any object within 30cm of its reach) which i made in my high school science fair(for these projects learn arduino programming language)
or maybe try to think of something out of the box or ask other peoples
