Hello,
The "best" flash I've used with everything from my Nikon F up through semi-modern bodies is the Metz 45CT-1 (or for newer cameras, use the CL-1).
The camera has a roughly 45m (!!!) GN and works in M and A. Absolutely nigh indestructible
and these days sell for about $100 used.
One really cool aspect of Metz flashes is that you can change out the bulbs in the flash when the termperature begins to degrade. That means that your major investment doesn't become a paperweight after x number of uses like, say a Nikon SB24, ect.,...
Just be sure not to hook it up to anything AF or with "lots" of electronics. It has been reported to be able to fry modern electronic cameras - although I don't know of anyone who's ever had this happen.
Good luck and let us know what you decide.