There’s no shame in admitting that you don’t know something. If you ever come across something you’ve never seen before, just ask. You may be surprised at what that thing’s function is.
These people needed serious help in figuring out what these weird objects were. So they did what any normal person would do: they asked the internet. Thankfully, there’s always going to be someone somewhere who has the answer to your questions.
“Chromed metal hand tool in shape of a plus. Possible instrument or scuba related?”

This thing almost looks like some kind of tiny crank, like those things you use for bikes and tires. But it has a much different use. Apparently, it’s called a sillcock key, and it’s used to turn sillcocks, spigots, and other water valves on and off. Interesting.
“Found on a beach in New England, roughly about the size of a wine cork. Might be made of some sort of ceramic, and has the same pattern of holes on each side.”

I’m not gonna lie, I would’ve just thought of this thing as a cork. But it does look different. Like, the same, but different.
And, as it turns out, it’s a propellant for some kind of old artillery piece. So yeah, it definitely isn’t a cork.
“What is this large Tic Tac looking thing next to a Railway crossing?”

If you look closely, you can make out the Honeywell logo on this thing. My first guess would be some kind of sensor.
And it turns out that that isn’t too far from the truth. It’s a radar sensor, which is used to detect obstacles that may have fallen in front of the tracks. How handy!
“What is this thing? It is about 4 x 2 inches and weights 2.25 ounces.”

Based on the Greek text on this thing, it either has to be some kind of ancient artifact, or it’s related to college fraternities. And it just so happens to be the latter, acting as a symbol to represent the Tau Beta Pi house. And it’s pretty old, to boot.
“Old house (maybe 1920s). Found in area with vanity and storage closet. Hand for size.”

The explanation for this one isn’t as exciting as I thought it would be. It’s just a shoe rack. From the looks of the metal rungs, it would probably be a great place to store high heels (which would hang on the metal parts).
“Strange nail? Found in my pool, thought it was from the pool cleaner but it clearly has only screws.”

I’ve definitely seen nails like these before, but I never knew what they were. Now, we all have an answer. It looks like one of OP’s neighbors may have recently gotten their roof redone, because this is a roofing nail. Now I’ll never forget what these bad boys look like.
“Crank-like object found in a restored old Irish cottage dating back to the 1700’s.”

This one really stumped me. I would’ve had no idea what this thing is. Thankfully, some people out there do. This one is a mechanism used to twist straw into ropes. This old house probably belonged to farmers, way, way back in the day.
“Small perforated metal table with a drawer found in Hungary.”

Have you ever played cribbage? If you have, you probably used a wooden board, one that probably looks a little bit like this .
But apparently metal ones also exist, and this is an example of that. The little drawer in the bottom is probably where all the pieces are stored.
“Metal object with handle like a cane, and some type of thumb wheel. About 10″ long and weighs about a pound.”

This looks like some sort of torture instrument, I’m not gonna lie. Thankfully, it’s a different kind of instrument: it’s a bone drill, or Trephine, which is used to relieve pressure in the skull by drilling holes in it. Not the best mental image, but at least it’s another mystery solved.
“Metal spheres, about 15cm in diameter and weighing 400-500g [~17 ounces] each.”

These aren’t balls, they’re boules (well, they’re probably also balls). These ones in particular look pretty old, but they’re still used in this day and age to play a French game called Petanque, which is something I didn’t even know existed until today. This one little mystery item sure taught us a lot!
“What is this S-shaped metal ornament on this house?”

Although this thing may look like a mere decoration along this building’s exterior wall, it has a functional purpose as well. It’s an anchor plate, made to keep the bricks against the wall. And really, there’s no reason for it not to look good while it does its job, anyhow.
“Huge old wooden hammer. Handle 30” long. Weighs 15lbs. What was this hammer used for?”

On the plus side, we already know what this thing is. The problem is more, what is this thing used for. And a wooden mallet of this size is apparently used to hammer stakes into the ground. The wood helps to keep the metal from deforming. Or, so they say.
“Real life looking eyeball, maybe glass? With 3 holes on the metal piece. Found at a flea market.”

Don’t worry, it isn’t a real eye (or at least I’m pretty sure it isn’t…). But funny enough, it’s a very specific item given out at a very specific point in time.
There’s a long metal piece on the back of the eye (not pictured), which is apparently supposed to act as a key chain. It was made by a taxidermist company. Weird.
“What are these circles on Guam island I see on Google Earth?”

The aerial view looks really cool. But in reality, it’s nothing new or unique. This is the naval base on Guam, and all of those little circles are actually much larger satellites. It’s been around for a while, and it would probably be a really cool place to visit.
“Found in a garage, around things [from] 1970-1990. Inside was hollow. There were two of them.”

This weird, antique-looking thing isn’t as big of a mystery as it may initially appear. It’s the top part of a ceiling light, like the thing that keeps a chandelier suspended. From the looks of it (and the fact that the poster says it’s at least 30 years old), it’s probably super tarnished.
“Woodworking or metal shop equipment. Gears, motor and electronic controls inside.”

You know how some shipped items have those poly straps around them? You know, those sturdy, almost plastic-like bands that are really hard to pull off of a box? Yeah, well this thing is a machine that installs those bands onto a box in order to prep it for shipping.
“It’s made of rubber (silicone?), stretches, and looks like it’s meant to be reused. What is it?”

It would probably take me years to figure out what this thing is used for, even though it has such a simple solution. As it just so happens, this little thing is a mounting strap, specifically for bike lights. If OP happens to have a bike, this could probably come in handy.
“Brass tube, all parts screw together. Has a scoop and a weighted end.”

This convoluted little contraption has a somewhat gross function. It’s a fishing priest and spoon. It’s used to, erm, give the fish its last rites (if you know what I mean). The spoon itself is used for checking and removing stomach contents. It’s probably really useful for fishers, but not so much for the rest of us.
“Metal, plastic, and canvas-looking fabric clips. They are a few inches long and some say FLATEX.”

The little clips could’ve been used for anything under the sun. But as it turns out, they’re specifically for holding up stockings and sock garters, and things of that nature. They look pretty old, too, which would make sense, since they were used long before the days of pantyhose.
“Opened up an old motor I acquired at a garage sale, took this part off the top and there’s a sponge and some wires inside. Why is there a sponge inside?”

If you don’t know anything about motors (like me!) then you probably won’t have a clue as to what this thing is. Underneath the foam is a starting capacitor, which is a part of a motor that gets it to spin a certain way.
As for the foam, it’s most likely there to keep the device from rattling.