One of the areas EA has hardly touched is investing.

Whether it is optimally investing capital now to be able to maximise the amounts of grants when the time is right (eg longtermist grants) or investing capital to create impact now (investments that create a net positive impact at a lower cost per unit of impact than EA grants). EA thinking is not yet applied in these areas.

The philanthropic capital which EA influences is highly impactful, but is still very limited in quantity, being only a small fraction of overall philanthropic capital. And philanthropic capital is only a very small fraction of total capital. 

If EA thinking can start to be applied to investing, the amount of capital used to create impact (although it will generally be less impactful than EA grants) could potentially raise the overall impact of EA by orders of magnitude.