Kodak D-76 Film Developer to make 1 Liter is a classic multi-use black & white film developer. It is economical to use and being a powder, the shelf life is nearly endless.
D-76 provides full emulsion speed and excellent shadow detail with normal contrast, and produces fine grain with a variety of continuous-tone black-and-white films. For greater sharpness, but with a slight increase in graininess, you can use a 1:1 dilution of this developer. It yields a long density range, and its development latitude allows push processing with relatively low fog.
The Brownie Camera Guy says:
I have probably used D-76 more than any other film developer. D-76 and Rodinal are my two classic multi-purpose go-to developers.