Wolfenstein 3D is said to be the grandaddy of first-person-shooters, and happily it runs well under DOSBox, with sound and mouse support.
It can be purchased through Steam. This version is configured to use DOSBox, though its data files can be copied and used to play source ports.
Wolfenstein 3D is open source, and can be played through the source port NewWolf for some enhancements. It requires all of the *.WL6 files to be copied from a Wolfenstein 3D installation.