There was an early flight combat simulator, I'm spacing it on the actual name. You could work your way up to choosing the top performing plane, "Paper Airplane" for some weird reason. But it turned you loose against an opponent in a boxed space and you had to fly and find them in a 3D environment. Wireframed planes. Amazing bit of programming for the day.
Not sure what else counts as a hidden gem. I'd say I spent more hours in Empire, playing five play-by-mail games at once, sending them to a friend on three time zones away, exchanging turns all evening by modem. Time-wasted more with Scorched Tanks, the shareware game, really fun, creative strategy and dozens of different weapons. Role playing, I loved Mega-Traveller, the Amiga single player version was quite good and took a long time to get through. Multiplayer, Gauntlet II with the 4 player adapter, true arcade quality dungeon maze crawling.
Those are my top picks.