Looking for cool inventions that can be 'created' in DnD
Hello! This is my first time ever posting on Reddit, but I have been lurking for a while so I'm sorry about any formatting errors. I have created my first ever campaign where my players will end up going to a 'Worlds Fair' but it will be in the outlands/concordant domain of the outlands so NPCs will be coming from all different worlds/planes to enter into the fair and show off what new potion/weapon/magical item they have created. Without going too much into the campaign (I love to ramble lol) I have been trying to develop this fair as much as possible, and I have been struggling to come up with a bunch of different inventions. Does anyone have any inventions they have created with previous characters that they don't mind me recycling in my campaign? Sorry for any grammar errors and thank y'all for reading!
Edit: I am looking for a wide array of inventions from smaller gadgets to large magically engineered items! One I used already from reddit was someone talked about how they made a proton blaster from Ghostbusters