If we can figure out how to fuse hydrogen atoms together we could make certain non-renewable elements. Helium is an example, not that its super important as an inert gas, but we do have limited supplies of it.

How exciting would it be to not have to pay much, if at all, for electricity? It would make electric vehicles far more viable, and if we could progress battery technology enough it would actually be viable to move away from burnable fuels for vehicles. The issue now is solar and wind are prohibitively expensive.