If you had to choose a single light shaping tool, you might do well to pick the silver Westcott 7' Parabolic Umbrella. First of all it's a really big, 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 design structurally as well. The shaft is double walled for strength, but it tapers to 7mm to fit Elinchrom and other European flash heads. Insert the shaft into the tilter bracket below the Elinchrom head. Older models or other brands may require separate purchase of an inexpensive umbrella mount. Instead of bendable metal, the 16 inner ribs are made of durable fiberglass and the fixed black backing ensures that all of the light output is on your subject instead of through the umbrella. The silver interior is slightly cooler in color temperature than a white umbrella and tends to focus the light into a soft but narrower field. You can also vary the light-to-umbrella distance along the shaft for a harder or softer light. This silver version is ideal for throwing the light over a long distance. Two of them, for instance could light an entire auditorium or a large graduating class. With the Westcott 7' Parabolic Umbrella less is definitely more.