> Aside, are the mega and giga prefixes ever used for anything except bits and bytes?

Sure, few examples of the top of my head:

- Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit!

- Similarly, energy consumption/production. Commonly used units MWh, GWh, TWh. Again, the proper unit would be J, not Wh. Or Mtoe, for Million tons of oil equivalent.