Lego, meccano, tonka toys, matchbox cars. But also books: Little Golden Book series, like The Color Twins; How and Why Wonder Book series, like Rockets and Missiles. Those books were magic.
And later, my prized possession, a Tamiya King Cobra slot car. Recently, I put it out near the sidewalk (footpath), in the original box, for someone else to enjoy. It still worked (tested with a DC source). Gone within an hour.
I still have much of my original Lego. My kids have passed through their own Lego phase, and my old Lego still fits with the new, even though Lego has obviously changed the molds and pocketing. The dimensional and colour stability of the old stuff is surprisingly good. That speaks very highly of Lego's engineering and process control.
Old and new Lego are now in protective storage, awaiting the next generation of little users.