If you had to choose a single light shaping tool, you might do well to pick the Impact 7' Parabolic Umbrella in translucent white. First of all, it's a huge broad light source that wraps light around your subject, yielding clean highlights and rich open shadows. But due to the special shape of the umbrella there's a unique mix of soft enveloping light with the kind of crisp detail you only get from reflectors. Put another way, if you combined a beauty dish with a softbox, you'd have a parabolic umbrella.
This umbrella has a unique structural design as well. Instead of bendable metal, the 16 inner ribs are made of durable fiberglass. The improved "finger-friendly" locking mechanism means you won't pinch your fingers when you're setting up or breaking down. The translucent white umbrella's fabric can be used in the traditional bounce mode, or for slightly snappier contrast and a low-ceiling-friendly smaller form factor, you can turn the umbrella around, aim the convex side of it at your subject, and "shoot through" by pumping the light source through the fabric. In addition, an optional diffuser is available for this umbrella, which effectively converts it to a large softbox with just a 1/2 stop loss of output.