For my work, it's AS350/AS355.
Flat floor is key. Ability to flip up rear seats is great, giving more room in the back when needed. Powerful, stable, and fairly easy to find in most major cities for charter. Lots of flexibility with door-off configurations, and many aircraft are equipped with sliding doors...great in winter time or for long transits to the shot location.
On jobs I work, it's always tech + photographer in the back, front unoccupied. I've worked out of most of the common aircraft one finds, and I'll take an A-Star or TwinStar any day.