Ask HN: Which toys best teach kids scientific discovery and critical thinking?

I'm head of a Los Angeles atheist organization. We're launching a weekly Toy Loan Center in partnership with Los Angeles County.

The County Toy Loan program is like a lending library for toys. Families are invited to borrow toys for free and return them a week later. Children are also rewarded with toys to keep when they return the toys on time and adhere to the program's code of honor. In addition to the toys the County provides the center, we will be adding donated toys that help foster scientific and creative thinking.

I'm stocking up on toys to donate now. Which ones best teach children about scientific discovery and critical thinking?

Keep in mind, these toys have to be durable and reusable. A lot of the scientific toys are one-time use, like growing crystals or chemistry sets or are very fragile. That won't work since we'd like to children take turns borrowing the toys.

Ideas to different kinds of toys and even direct links to Amazon and other online stores would be appreciated. Also, toy companies that specialize in these types of toys would be good to know. I'd love to directly support specialty toy companies.

Thanks!