suggestion

for the stone age ppls ... I would suggest sewing machine, electronic cutter and gun. as u know, clothing, food and housing are the most important things for the stone age ppls. they need the sewing maching to make their clothes; electronic cutter to building their homes and gun to hunt their foods.

I think you'd need electricity first before you can use "electric sewing machine and electronic cutter" : )

So how about an electricity generator first?

Another tool would be a lighter to start fire.

Last but not the least, a telescope / binoculars for them to see far away. It will make it easier to look for animals or enemies.