My favorite flash is a non-dedicated Sunpak 383 Auto ($79.95 from B&H photo). It's a bit large but is extremely versatile. It has tilt and swivel, plus three auto-exposure modes -- f/16, f/8 and f/4 when using 400 ISO film. It also has manual modes of 1/2, 1/4, 1/8 and 1/16 power. And it has a PC cord to attach to the Nikon SP PC socket (remember the days when PC had nothing to do with personal computers?) However, over time, this PC cord can become unreliable, so I always carry a spare hot-shoe-to-PC adapter just to be safe.
For family shots indoors, I pretty much set it on f/4, bouce off a ceiling or wall, open the lens to f/2.8 or 3.5 if that's the maximum aperture, and then shoot away. A shutter speed of 1/8 to 1/30 provides nice ambient fill.
Flash on a rangefinder is a joy to use ... Unlike SLRs and their mirror blackout, you never wonder if the strobe fired.
Attaching some recent examples with Nikon SPs and S3s . The candlelight shot was with a 50mm/1.4 lens wide open at 1/8 with the flash shot at 1/16th power manual and bounced off a far wall. The picture has some camera shake, but the flash froze and sharpened my daughter's face. The birthday picture was shot with a VC 25mm/4 shows daylight fill flash. The tree decoratiing was in a very dim room lit mainly by the tree lights. It was shot with a Nikkor 28mm f/3.5 wide open.