Fired and unfired pistol, rifle and shotgun ammo. I think I could give an interesting talk on the differences and the history of various cartridges, no fine details, only a broad overview. To keep it fun, I'd sprinkle in lots of things most people probably don't know.

For example, did you know an AR-15 round is actually kinda wimpy, especially compared to a typical hunting round? In some states, ARs are illegal to hunt with because the bullet is deemed too small to make a clean kill. It's basically a hauling ass .22.

And .22s are a neat topic by themselves. There's crazy variety out there, even tracers!

My fully water cooled itx PC running arch, then I can force my hubby on them 😍

cat

Not sure what a show and tell is, I guess my laptop with tons of stickers, and boot up something that looks hackery. Besides that, my guitar perhaps?

I'd bring some beer that I make in my garage.

Probably a synthesizer. MEGAfm would be the coolest, but I imagine my desktop Hydrasynth would be more impressive.

I'd bring my Moog Theramini. Nothing like playing the air waves! It's magic science!

My autograph collection.

My knives, because it's sort of weird even for me that I carry these knives around for work, and a weird thing becoming humdrum is the sort of thing I'd like to hear about at the show & tell.

Probably either a Ken Payne bronze called The Trail of Change or my Ibanez s521 guitar with the ocean fade paint job.

Inherited it from a family member who loved southwestern and native American culture and history they shared with me so it's some sentiment along with an interesting statue.

Most of what I own is minimal and function over form but I just think it looks awesome and is fun

Climbing gear or 3d printers.

Probably my chi-fi headset. Don't really have anything to show off. And maybe my laptop to show that I use a package manager of the future.

Professional level landscaping accessories.

Folks always seem fascinated by my keyring.

My papercrafts.

Depends, is it a casual thing or more serious? If it's casual I'd probably just bring a Trading Card Game deck (MTG, YuGiOh, Pokémon). If it's more serious, I'd bring in some of my junk like a broken microwave magnetron, to simultaneously bring attention to the problem of short product cycles, explain a bit about how what most people see as a magic appliance functions, and show that even complex things can be broken down into simple parts.

You know, I think an adult show and tell wouldn't be too different to a kids one, we don't change that much in what we find cool from 7 to 70.

I'd bring some pets, I have geckos that are an all female species and reproduce only through parthenogenesis, most people find them cool.