This is a list of toys that my kids have played with on a consistent basis for many years, from the time they were toddlers until their tween years. They are high quality, creative, and open-ended, which makes their appeal last for a long time.
These were great from ages 1-7 or so.
Just when I think I've cleaned this up for the last time, my kids find the container of kinetic sand at the bottom of a drawer and gleefully get it out again. It's so pleasing to work with (and vacuums up well).
Kinda spendy for colored pencils, right? Well, maybe. But these have lasted us about 5 years with heavy use. They sharpen beautifully, go on smoothly, and come in lovely shades.
Doesn't have to be this one, of course, but matching games last a long time. When they're very little, you can simplify by using a smaller subset of the cards.
If your kid likes LEGO, this will never be enough on its own. But it's a good starter set.
The name brand here is magna tiles, but these picasso tiles are just as good. They've lasted for years. And any toy that has your 3-year old saying "equilateral" and "isosceles" is a winner, right?
You cannot have too many of these.