Good toys for a toddler that are not baby-ish?

Hi! My cousins birthday is coming up and I'm not sure what to get him. He's turning 3, is very intelligent, and smart. All of the toddler toys I see are too babyish... He'd want some sort of building... lego... K'nex... or Structure type of toy. I'm looking for something durable and less than $50.00. Please let me know any suggustions! Thanks!