DS is 5, and the toys that have gotten the most use are his bike and scooter (and before this his balance bike). Balls get a fair amount of use, but most of his hours spent outside are playing with whatever he finds in nature - dirt, sticks, rocks, and the like. The best outdoor investment I have made for him is a pair of rain pants to put over his normal pants so he can do what he likes outside without me chasing after him to keep his clothes clean. He has an uncanny ability to find any little spot of mud and sit right down in it.