I've been fooling around with my smallest umbrella lately, trying to figure out how I can use that as a single light source. Or to be more specific: How I can use it to create both soft and hard light, i.e. get deep shadows.
With more professional equipment (i.e. something larger than speedlights) I guess I'd go for a beauty dish, but a reflecting umbrella almost does the trick too.
These two self portraits are lit exactly the same, the only difference -- obviously! -- is that one is a profile shot, the other is straight on. The light source is almost right above. It's quite literally what I'm looking at.