Freespace 2, currently free on GoG · 10:31am Sep 26th, 2019
Highly recommend you nab this one if you haven't played it, even if you've never heard of it.
It's one of those rare bits of media so good, that it basically killed its own genera for decades. Even today, you seldom see space-fighter games, and the very few that pop up almost unerringly get compared with this one gold standard game.