I remember going out to the creek and looking for crawdads and turtles, picking up and turning over every rock and finding them hiding.
Laying outside at sunset watching the sun go down and the clouds float by. If it was just right you can see the sunlight reflect off of high flying jets as they went over. Speaking of that, using a pair of strong binoculars or a telescope that didnt turn the image upside down and watch them up close as it flew over.
Same goes to the comet that took its time going by earth back in the 90's that took several days to pass. Go out every night and look at it with the same as above and be amazed on how it looked and take in the wonders of space.
Waking up on saturday morning just to watch the cartoons that were on from 7am till noon, then going over to a friends house to play and work on the treehouse. Playing hide and seek all hours of the day with the only worry of what time you had to go home to eat supper.
Back before cell phones were the thing, we thought we were awesome when we got our first set of walkie talkies. Those things were completely cool that we can be a block away on our bikes and still talk to one another. Oh, that and putting playing cards in the spokes of the wheel to sound like you were on a motorcycle.
Some of the funnier things we had done were to beg our parents to get some of that huge sidewalk chalk, just to use it all on the road to make one huge chalky area, just for cars to go through it and make chalk tire tracks down the road.
When winter was here, snowball fights, finding iciciles and eating them, and on the rare occasion to make an obscene snowman just for the heck of it (we were pretty onrey sometimes)