Build a Tesla turbine from 2 old computer hard disk drives using basic hand tools and a pillar drill. No metal lathe or other expensive fabrication machinery is required and you only need some basic craft skills. It's crude, but this thing can scream!
Tesla Turbines promise up to 92% efficiency of converting air or fluid flow to rotational energy and its use can also be inverted for use as a pump with exceptionally high efficiency too. With compressed air becoming recognised as a feasible form of energy storage, we can see this device in everyday life soon as a source of locomotion. Factoring the simplicity, robustness and resillience to ingress of this design and you have something ideal for pumping heterogenous fluids like sewarage or fluids with suspended particulate. As a pump, this device has an important role to play in the developing world. More about it here: http://en.wikipedia.org/wiki/Tesla_turbine