Well there's essential oil of cannabis, which I think is what hash oil is, technically, however even a hemp oil or other high quality oil extract/emulsion of fine cannabis can have helpful medical applications, such as for physical pain, skin conditiuons, etc.
Remember, some components of cannabis are oil soluble while some are alcohol soluble and others water soluble.... w/ 420 or however many different components to cannabis, who knows which ones have which properties, under what extract conditions, etc., other than the well studied and much loved delta-9
Concentrated forms of thc is one thing
I've found that there is only an indirect correlation between THC and pain relief capability - for my particular condition anyway. In other words, some strains will get me very stoned yet have minimal effect on the pain whereas certain strains have a higher 'pain factor' w/out getting stoned beyond functionality. It's a hard line to find, to be as pain free as possible and not completly blitzed - I'd love to find a high 'pain factor' low thc strain, personally....
I love the idea that if cannabis were just discovered by (rational) humankind today there is little doubt it would be touted as a miracle medicine...