Don’t forget the hypnotic appeal of playing with rusty sharp throwing objects : Jarts! That was the best game EVER!
I saw plastic army men mentioned but I just wanted to expand on that. They sell them at the dollar store so you can get a whole Division’s worth for a few bucks and the provided me with hours and hours of fun. I used to set up elaborate battles complete with trenches, bunkers, and hills, have the battle (this part was actually the fastest), and then set it all back up again.
I’ll also echo that large boxes are great.
The natural world is also full of great toys. Don’t underestimate the value of sticks, mud, and good dirt. There are all kinds of games that can be played with those. Acorns too. Acorns are great for stockpiling and then having a massive acorn war with (you had to break off the pointy bit though). Also if you live in the right part of the country you can sometimes dig and find some good clay deposits. Those were lots of fun.
An all-time favorite with the grand kids has been Marble Race. We bought a couple of boxes almost 20 years ago, and they still get drug out anytime any of the kids visit.
Every Friday my second-graders have Ketchup-and-Mustard. Students who haven’t finished their homework or turninable classwork during the week get to ketchup on it at their desks during this time, while the others get to play with their choice of blocks, games, cards, or art supplies. (I don’t know why it’s mustard. Shut up. I stole the idea from another teacher). My point is that the Legos get more play than all the other supplies combined during this time. When I give kids a chance to share their creations afterward, virtually all the sharing is of Lego creations. I probably have $30 worth of Legos in the class, and that’s enough to keep about 10 kids occupied simultaneously.
FWIW, although I like how the fancy sets look, and although those are what I spent my allowance on when I was a kid, the much better bargain is the $20 massive generic tub you can find at the store. The kids have no problem projecting their imaginations onto the rectangular prisms therein.
There were two other toys that provided endless entertainment when I was a kid. The first were blocks and marbles. These blocks have holes cut in them that marbles can roll through, and you can spend hours building complicated pathways for marble transportation. They’re tremendously fun.
The second was super-cheap. I went to a Bible Church where communion was courtesy of Welch’s, and they served it in these tiny clear plastic cups that probably held about a tablespoon each. Afterwards we would zip around the church collecting all the discarded cups, take them home, wash them out, and build tall structures out of them.
Daniel
Very simple, really. Try carefully wrapping the wire through the threads of the adaptor, taking care not to let the wire kink, or slip out of the grooves, or else the whole thing ends up needing to be rewound.
Sure, it’s fun. If you have a lot of patience, a good sense of meticulousness, and the yet undiagnosed foundations of obsessive-compulsive disorder quietly simmering in the background.
I was the childhood master of making toys of out trash:
An old bucket - fill with plants, dirt, snails and make “soup”
Discarded toothpaste boxes and the like - cut and tape into rocketships
Plastic grocery bags - action figure parachutes
Sticks and flower stems - make into bows and arrows. I actually could shoot a stick about six feet with these.
Fabric scraps - Like others, I made troll clothes out of these, and also troll beanbag chairs.
Looking back on that list, I was quite a tomboy!
As for actual toys that are purchased, I will add to what people have said above:
Plastic dinosaur figurines (I spent hours and hours playing with these, they were my favorite toy)
Those styrofoam airplane gliders you got at the dentist’s office
Fingerpaint
Silly putty
and (the biggest hit among my little students)
the Slinky!
A couple more things that kept us occupied: making collages. A cheap scrapbook, a bottle of glue, scissors, and a stack of magazines. Assemble a Work of Art on each page. (I made an Eyes page with nearly 200 pictures of beautiful eyes arranged in a spiral.) For younger kids, let them stand on a chair at the sink and ‘wash dishes’ (anything unbreakable) - makes a big wet mess, but kept mine busy for hours; and, “Potions” - a plastic container with a tight fitting lid with a little water, a dash of this, a dash of that (instant coffee, ketchup, mustard, old spices, vinegar, salt…) mix up your potion, shake well, make your mom and dad smell it and watch them faint!
I remember well chunks of scrap wood, cut into blocks, some long, some short - there’s something about BUILDING a structure that’s ingrained.
Damn, I want to be a kid again. I’m going to buy me a coloring book, and this time I mean it.
Another one that us kids liked was whiffle ball. It was easier for the little kids but still enough fun for the older ones. Nobody ever lost an allowance by breaking a window with a home run ball either.
We also had a croquet set, a volley ball and net, a badminton set, our mitts, balls and bats for baseball or softball and an old football we tossed around. Oh, yeah…and hula hoops, jump ropes, sidewalk chalk and ball and jack sets. Most of us didn’t participate much in organized sports, but we sure played outdoors a lot.
I think that’s probably how my mom stayed sane. 
Oh you just reminded me of one of my favorite childhood games. We yest to play Extreme Croquet. Basically we’d get the normal croquette set and set up a course full of obstacles. There were ramps you had to go up and down, brick walls you had the bust your way though, holes you had to jump over, and all kinds of fun things. Of course this did not add a great deal to the life of the set in question.
Coloring books and crayons were fun, as were toy cars. Playing outside in the dirt was also a lot of fun. It helped that my parents had almost 5 acres so we could tear up a small area of the yard and they wouldn’t really notice or care. Until I was almost 8, I enjoyed playing with empty bottles in the sink, and pretend to do the dishes. Probably why I love to wash dishes by hand as an adult. We also played croquet and bocce ball.
Another fun thing, but probably more dangerous, was playing with all the scrap wood left over when they built our house. We would build ramps and ride our bikes over them, and build benches out of some cinder blocks and wood planks. Kick ball was also a “family” thing. My father would be the “pitcher” and my brother, sister and I would play. We used trees and the corner of the house as bases.
My little brother broke two of my grandparents windows with a wiffle ball. My father broke the same window twice in one month. These were also old 1950’s style plate glass windows, not modern ones, so I don’t know if that has anything to do with it or not.
We’d always be pestering our small-town appliance guy for boxes. When we got one we’d do stuff with it in the yard until it was too beat up for that. Then we’d tear it up into big pieces and take it down underneath the bridge that went over the train tracks and slide down the embankments. Summer sledding!
Other staples of our play life: Blocks, yardsticks (to make ramps with the blocks), ball bearings taken from train sets (to roll down the ramps), dolls, old blankets and clothespins to make tents on the clotheslines, cards for playing card games and building card houses. The sandbox. Especially if you had a water source.
It’s Log, It’s Log, it’s better than bad, it’s good! 
Another good thing is a waterhose and either one of those kids sprinkly things or just a regular old lawn sprinkler. Or you can fill a big tub or kiddie pool and let 'em at it.
Rubber band guns made out of pencils.
Lego… back before all the pieces became so specialized. We had all the old “Space Lego” sets. While not inexpensive, the value for money was astronomical as we played with that stuff for years.
If you can get hold of a thin plastic bag like those from a grocery store, and strip some palm fronds you can make your own. You’ll only need to buy the string (sewing thread) - and get this - no glue is required - you take a small rock and hammer the plastic together! Cut your traditional diamond kite shape, tie your crossed sticks together in the middle, then hammer small strips of plastic by the corners to hold the sticks to the diamond. Woo hoo. It won’t last forever, but building more is part of the fun. Don’t forget the tail.
You can make up a lot of games, both indoor and outdoor with nerf balls of different types. I will second the basic old tools and scrap wood suggestions.