What's a good remedy for a dry hacking cough?

Depends on the cause. A person with a persistent dry cough can be evaluated by a doctor to see if antibiotics, asthma meds, or allergy meds are needed. Possible causes include viral or bacterial infection, the flu, mild "whooping cough", regular pneumonia, "walking pneumonia", allergic problems, asthma, etc... People with very mild, non-persistent symptoms sometimes find the otc allergy and cough meds helpful.