I think that philosophers of language have overlooked issues in semantics that they really should not have overlooked. My main thing is plurals. For example, Cappelen and Lepore stick a bunch of plurals in their basic set by claiming that the singular indexicals (I,he,you,etc) and ‘all their various forms’ (approximate quote) are as well. This overlooks the ways in which the plurals are different from the singular. For example, in the first-person case, it looks like ‘we’ is not automatic while ‘I’ is. Nunberg has some interesting examples of ways in which ‘these’ and ‘those’ differ from ‘this’ and ‘that’.