@anthracite I honestly would suggest X:Com Enemy Unknown/Within (the first of the current gen x-coms) its good for drilling in small fire-team tactics like cover, flanking maneuvering, situational awareness, and how important logistics and intel is to a fight. Since I've got most of the missions and variations locked in, I know what my force requirements are, and what roles are always important to have highest ranks in.
@anthracite And there is a pretty decent mac version available, and its on consoles too.