A non-exhaustive list in no particular order:
Science branched out from philosophy and the scientific method is a creation of philosophers, on which many people (of course not ALL people) agree.
Descartes' cogito presented a solid basis for modern philosophy.
Leibniz' idea that we share the same world but see it from very different perspectives, and thus we all have our little piece of truth, which might differ from one another due to our different positions in the world.
Kant's distinction between noumena and phenomena founds modern epistemology.
Popper's falsifiability rule (+ subsequent refinements by Kuhn and Lakatos), and his rejection of totalitarism and determinism.
The rejection of sexism and racism as ill-founded, exploitative and morally wrong.
The importance of structures that are "more than the sum of their parts". Aristotle alluded to it, and the German gestaltists, and then Levi Strauss and Bateson expended on it.
Socrates' demonstration of the philosophical mindset as learning to question the boxes that we think within, to tease out presuppositions for examination.
Tied to the above, all the axiomatic work on mathematical and logical pluralism.
The stoics and pragmatists acceptance of uncertainty as intrinsic to life and philosophic knowledge.
Linguistics.
(Edited based on @dcleve's comment)
Postface
Thanks for the encouragements. Dcleve noted the basics of philosophy:
Socrates' demonstration of the philosophical mindset as learning to question the boxes that we think within.
Chris Sunami made a similar point:
Philosophy, by nature, is the study of questions around which there exists no widespread agreement, shared framework of inquiry or self-certifying means of confirmation. [emph. added]
The list above now strikes me as all (or most) about what they are talking about: framing (deframing, outframing, reframing...). Looking for the basic axiomatic of a world view, and questioning and studying these basic presuppositions.
When Descartes makes the mind experiment of the cogito, when he imagines that he can doubt even the belief in a real world around him, he is looking for a sure and certain axiom upon which he can logically reconstruct the certainty in everything he pretended to doubt. And he finds it: one cannot doubt the existence of doubt, hence of a doubter, hence of a Creator of the doubter, and hence His creation is real and I can trust my senses 'cause God ain't no cheater (in short).
Descartes was testing the solidity of the frame of individual existence.
With his monads, Leibniz was building a frame of reference for the world as perceived by all of us (including animals), a world in which people's views are always derived from a certain geometric or intellectual point of view, a perspective. It's now banal to say this but he formalized it.
Linguistics derive from an analysis of the very tools we use for thinking: signs, symbols. That too is a frame.
When Martin Luther King dreams, he is reframing his country.