/lit/ - Literature

Kant and Hegel, or German Idealism more broadly, is a pretty decent way to go as it offers variety in subject matter, recognition and mutuality with many other subspecializations in philosophy (analytics and continentals, moral philosophers and philosophers of language, etc all know some Kant), and always has new ideas being written about it. I was considering doing a PhD in philosophy and I was being advised to pursue studies in German Idealism. Specific figures in the history of philosophy from before then (Spinoza) would be too specific and would pigeonhole you in doing history of philosophy, and specific figures from after then would place you too firmly in either the analytic or continental markets (with some cross-over possible for Heidegger and Wittgenstein (and of course Nietzsche if you don't count him as a German Idealist), but none of those damn Frenchies).
Philosophy of Mind is pretty big and has a robust presence in most top departments, but it seems very narrow -- you sure as hell wouldn't be able to study Kant, Hegel or Spinoza there.

But seriously, don't listen to /lit/.