Can you list some gadgets and inventions to make?

Can you list some gadgets and inventions to make from science fiction? I want products that everyone wants, it must be marketable, list as many as you can. Thanks.
Update: in the name of jesus: You know what? If you want to fight with me, go ahead but don't bring Taeyoung in here because he doesn't deserve your trash talk about him, okay? And the person who will die with a cancer might be you, not others.
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