Do you want on camera, or off camera flash? On camera, no one ever went wrong with a Vivitar 285, or the older 283. Metz and Sunpak also made/make powerful on camera units.
I am partial to separate handle mount head , and pack and head flash, since bouncing or soft box diffusion and reasonable depth of field apertures with my medium format cameras needs a bit more of a whomp on occasion than 4-aa battery powered units can muster.
For handle mount I have a Sunpak 522, which is nice with a range of auto apertures, and manual dial back capabilities for fill use.
In the reliable older pack and head class I have Metz 60 series CT1/2 (#2 head, #1 pack, with multiple auto settings, and a lot more flexibility with a mecamat remote sensor) (100iso GN 160 in feet), an ancient Braun Hobby EF300 (GN about 150, with full and half manual control) and a Norman B200, (which at 200w/s with the reflector is GN about 160, and can be set to 200, 100 or 50w/s.
I would recommend you see what 'the strobist' web site is talking about before you commit to any grand ideas of what gear is really needed to get the shots.