What's a good and yet modest present for a 5-year-old boy?

I don’t know the child, other than that he is apparently a healthy, normal smart little boy.

Let’s say in the $10 – $20 range.

It’s been a very long while since I was tuned into what’s cool for little kids. Actually, I don’t really care whether it’s “popular” or not, just that he’s likely to enjoy it. However, I won’t buy anything that’s tied into TV or movies.

Oh, one other thing: it’s best that it not be something dangerous to have around when there’s also a toddler in the house; for instance, marbles or Legos or other tiny swallowable things.