This is by no means an exhaustive list, I am certain to be missing dozens of people -- feel free to add suggestions in the comments!
I am consciously excluding the Hitchcocks of the world, because appearing on screen isn't necessarily acting. So no, cameos don't count. I'm also limiting it to things that are listed on Letterboxd.
Generally speaking the film included is one from the side of the actor/director backslash for which the person is less well-known (so David Cronenberg is here as an actor, while Scarlett Johansson is listed as a director). I've mostly tried to pick projects where the actor is not directing themselves. If you think Jordan Peele is still better known as a performer than he is as a director, I totally get that. Just going from my gut here.
Please don't yell at me if I forgot someone, my brain is human-sized not internet-sized.