Here's an argument against mind-body materialism that I find persuasive:
1. If Materialism is true, all possible minds are physical brains. (Premise)
2. Abstract objects are necessary concepts of a mind. (Premise)
3. There are possible worlds in which there are no physical brains. (Premise)
4. Therefore, Materialism is false. (From 1 - 3)
I take (1) to be one of the standard interpretations of Materialism, but of course, there is some variance among those who call themselves Materialists. (2) entails conceptualism: both the necessary existence of abstract objects and their conceptual nature. One of the inferences to be drawn from (2) is that a necessary mind exists. After all, abstract objects cannot be grounded in just any mind, since there there are possible worlds in which you and I (contingent minds) do not exist, and yet those same abstract objects are still instantiated. Moreover, there are possible worlds in which nothing contingent exists.
Given (3), conceptualism provides us with a strong defeater for Materialism. Obviously each of the argument's premises has to be defended. This is just an outline.