Right now I can't think of a philosopher who is as imposing to me as (the late) E.T. Jaynes is. Unless you count people like Judea Pearl who also do AI research, that is.

That (Jaynes) is a pretty high standard. But not impossibly high. As candidates, I would mention Jaakko Hintikka, Per Martin-Lof and the late David Lewis. If you are allowed to count economists, then I would also mention game theorists like Aumann, Binmore, and the late John Harsanyi. And if you allow philosophically inclined physicists like Jaynes, there are quite a few folks worth mentioning.