Essential - cooking, baking, bread making.
Brewing is another basic skill that produces a product that can be used for barter.
Farming / growing crops - how else will you get the grain/fruit for cooking?
Hunting - obvious one there. But the other side of that coin is butchering. How many butchers do you know?
Sewing, to repair clothes that won't be replaceable for a while.
I could go on.