Olympus FL-50 on OM-D

I have one and it is my go-to flash for large venues (big meeting rooms, high ceilings, bounce flash). Anything with less power will just not do the job.  It will also give great fill flash for bird photos outdoors up to 50 feet away used with a Better Beamer.  The FP TTL mode is also very useful to keep shutter speed up when shooting birds and other wildlife.

It is a little large, but I have become accustomed to carrying it in a "cradled across my forearm" fashion between shots.

I also use a Nissin DI466 for bounce flash in normal-sized rooms in homes with eight foot ceilings.  It is easier to handle, but is just not powerful enough to use as a bounce in large meeting rooms (think 50 feet wide, 10-12 ft ceilings).