I would agree with dswithers. Handstand pushups are HARDCORE and hit muscles all over your body, but if you can't do those then I would say dumbell military press (for shoulder ROM and developement) or standing barbell military press (great core/shoulder movement).
Sorry, but research has blown away Behind the Neck Presses citing the many contradictions with shoulder capsule health, RTC strength, and cervical injury risk. If you stil do these and think they are okay to do, its simply becasue you haven't got injured...yet.
Take it from a guy that had did them for years and had RTC surgery 3 years ago.