Who knew that tetrahedra could fly? I know, pretty much anything can fly when you fill it with helium, but the movement of helium-filled tetrahedra called SmartInversion by Festo gives rise to an interesting and unusual propulsion method [source: gizmag]. Using inverse kinetics, Festo have developed what they call an "airborne geometrical band with inversion drive". The movement is difficult to describe but mesmerizing to watch:

Tetrahedra also play an important role in Computational Fluid Dynamics (CFD), helping simulate air flow by providing the mesh around complicated geometry so a CFD solver can generate a solution.

Tetrahedra Mesh: Created by Caedium

It's good to see tetrahedra breaking out on their own from CFD in order to carve out a new niche in real world aerodynamics.