The Wing Commander 2 Demo is an especially impressive affair. It isn't playable, but it runs through an early version of the game's introduction... complete with early, different, artwork for the Kilrathi palace! It also features ships in the Wing Commander I engine, including an even earlier version of Thrakhath's Bloodfang fighter. You can download the demo here (2 megs)--run it in DOSBox! There is also a video of the demo available on YouTube.