A bit of a different answer:
In the fighter world -
HF: When talking to the guys on the ground BLOS, until we get close enough then we go to UHF. But most of the time its SINGARS or SATCOM. Otherwise its the tankers talking on HF when they're dragging us across an ocean somewhere.
VHF: within LOS to each other
UHF: within LOS to ATC or each other
When you're on the ground talking to other ground guys: HF via NVIS mostly (but you have to look up a bunch of space weather crap to figure out the best freqs to use given your location to location geometry and time of day, etc).