Super late to this thread but I really enjoyed it and it brought back tons of memories of my own. Loving the nostalgia. Here we go...
Getting excited about stickers.
Magic The Gathering (yeah I was a dork). Anyone else?
Capturing and torturing small insects during recess.
When illegal fireworks were dangerous and exciting. Finding random things to blow up.
Of course, finding shredded porn mags in the woods (actually the bushes in the park with a secret path leading to a clearing). Getting props for sharing the secret bush porn with friends.
Whiffle ball in the driveway with random landmarks as bases and the outfield was the middle of the street. You had to run into traffic for line drives & fly balls. Hitting it deep enough into the shrubs usually meant an inside the park home run - eventually had to rule that a foul ball.
Playing "pickle" in the rain and sliding around in the mud for over 4 hours despite Mom's warnings, then catching pneumonia and missing the last 2 months of the 6th grade.

on Super Soakers - the ultimate Summer Vacation game changer when they dropped. I had the 100 - good balance of power, water capacity and mobility.
Home made slip-n-slide using the black landscaping tarp from the hardware store.
One inch punch game - inspired by Bruce Lee.
Creating random games on our block that involved throwing things at each other (fruit from a neighbor's tree for example).
Capture the Flag

on He-man, Muscle Men, Transformers and Legos. Also, Battle Beasts, TMNT and Star Wars toys - both the full sized action figures and the miniature models made of metal.
Looking forward to the State fair every year. After a long night of hitting all the crazy rides (the mega sized swings and Gravitron were favorites) I'd lay in bed, close my eyes and feel like I was still on a ride, then dream about rides all night.
Spending way too many quarters on Street Fighter II at the comic shop, then the chipped/hacked turbo version, then Championship edition. And then that one Summer when it was finally released for Super Nintendo and we could play forever for free.
Bike rides as an excuse to go to a safe secluded spot to smoke out (usually by the levy).
When the ultimate place to hang out was the garage. Ping-pong, darts, and it was easy to hide beers and weed smoking from the parents.
So many memories. I miss having all that free time to just be creative, get stupid and have fun with friends.