[dworin]

As a user more than an engineer, most of the apps I use have 'one feature,' but the one feature that's important to me is different than the one feature that's important to other people. My 'one feature' may also be a unique combination of smaller features that, when brought together, solve one very important problem for me, and some different combination of smaller features in the same tool will solve a different problem for someone else.

[khedoros]

Agreed. When I seek out a new program, I usually have some specific goal that my current software doesn't cover, which usually means that it's something fairly "out there", and not even necessarily a core feature of whichever software I find.

Still, a program needs a guiding light to its design. It has at least one purpose, and that purpose should be the central focus of its design. That doesn't mean there can't be ancillary features, of course.