We made up a few that were fun.

First was cowboy and Indian block fortress wars. I had a big set of wooden blocks, like leftover 2x4 and 2x2 actual lumber pieces among other pieces, and a set of plastic cowboys and indians. We would split the blocks up and each build a fort, then place our cowboys or indians at various spots on the fort. Then we would take turns throwing a block at the other person's fort to make it fall apart and the plastic guys fall. Once you knocked all your opponent's pieces off their fort you win.

I also had a big set of cheap Lego knock-offs, they weren't hard like Lego, they had a bit of flex. We would build cars with them and we each got a certain number of wheels we could use. Then we would crash our cars together head-on, parts would go flying but they didn't break like Lego would. After each crash we'd check to see that each car could still sit on the floor without any part of the body touching the floor, the wheels had to keep the car off the floor. If both were good we kept crashing them together until someone's car lost enough wheels or parts that it was dragging the floor, then they lost.

And finally my friend's house had a big carport with a flat metal roof on it, probably 20x40 feet. Over the carport was a gum tree, they drop pointy ball seeds a little smaller than a golf ball but not as hard, and the spiky points aren't particularly sharp. There were thousands of them on the ground and roof. One of us would get up on the carport roof and the other would run around on the ground. We threw gumballs at each other and if the person on the ground hit the person on the roof we would switch places. Can't believe neither of us fell off the edge of the roof. At one point we made a sort of hand-held catapult by nailing a plastic container to a ~3' piece of 2x4 lumber, we'd fill the container with gumballs and fling them at the other person all at once. The person on the roof usually got that since they had less maneuver room up there.

Good times.