Terminal Velocity! Great game. Feels natural with a gamepad, has fun missions, and seamless tunnel sections. One of my favorites.
I'm tempted to download that. Though waiting for the GOG treatment is tempting too. That page on 3drealms gives me hope that all of those games will eventually be on GOG.
(I have the original CD-ROM somewhere, maybe. I've moved since then, so it might not have made the trip.)