I have a pretty dull, comfortable desk job and lack the imagination to come up with any. Can you name some?
(I've been wrong before when I was skeptical when everyone was hyped about iPad, Deep Learning, etc. so please convince me about Apple Vision, Mark's metaverse, or google's glasses and paint what might be in 5 years.)
The HUD could overlay SKU, product description, weight, volume, etc — directly onto the actual item in the storage rack.
Even an artist (make a sketch, blow it up a 100x using AR on a wall, trace paint to keep proportions right - heck the artist doesn’t even need to do it themselves, they could hire an associate to do it).
For 3D artists it presents as a more intuitive way to sculpt models. For automotive designers, it allows a cheaper and faster means of iteration, given that such a task requires a much better sense of scale than the one given off of a monitor. Same goes for architecture, which when coupled with a game engine, also allows the customer to preview their future house.
(props for being open to ideas btw)
Security guard at the mall, Power Rangers, etc...
Fun: I want a HUD for skiing that marks where my friends are and warns me of rocks / cliffs / incoming weather.
Most people don't want it for games and porn either -- although those two things are the only obvious mass-market applications.
There are lots of other real uses, but they're all niche. It's hard to come up with a real, mainstream use that would drive adoption in the general public.
It might sound mundane, but the hope is that one day slipping on a pair of glasses outperforms conventional monitor technology.