Water has the ability to heal, earth can bend metals, and fire has lightning. I am not sure if I missed what air had if it has any sub skills.
Each sub-skill is a relatively rare skill compared to the population of that type of bending that requires special training (with one exception) to learn. As the population of air benders has been tiny and many nuanced details of the form have been lost over the centuries. Aang was a good airbender but likely didn't know everything as he was a child. From this we can speculate that if there was one, it may have been lost.
I have not found an example in Avatar nor Korra but I'm a little behind on Korra (which is why I didn't answer quickly).
We can speculate many different interestng ways manipulating air could be specialized for different uses: sound bending, foam bending, breathe stealing, rapid oxidation, elemental separation, forcible phase transition (that could get gory), etc. This, however, would not have any canon support.
Breathbending (or something of the sort; taking the air from someone's breath/lungs). As seen on The Legend of Korra, Season 3 Episode 10: Long Live the Queen
Climate control? It’s already been said by Tenzin, that Airbenders can control their body temperature through breathing techniques, so i think that it’s feasible that they’d be able to manipulate/control the temperature of the air around them as well. Although, within reason. Like they’d theoretically be able to cool the air immediately around them to a certain degree in a warm climate, but not drastic changes such as making it cold near an active volcano. We’ve already seen benders do it. Earthbenders with lavabending. Waterbenders with icebending. Firebenders clearly can bend different temperatures of fire (as seen with Azula’s blue fire).