HereForTheBeer: These don't quite qualify with the spirit of the thread since I have seen each one mentioned here. But mentioned only once that I recall:
Lightspeed, a space combat and trading game from, um, late 80s? Something like that. I utterly sucked at it.
D/Generation. I'm really fuzzy on the details. Future or sci-fi, maybe an action puzzle game? Think you had to puzzle your way through rooms that had various devices set up to kill you, and you had to figure out how to avoid setting them off or something like that. That description is probably not right... Another community member did a remake titled E/Generation, so try a search here and you can find a link to the remake.
Got a third one but I'll have to find it on MobyGames before posting.
Lightspeed was by Microprose. It has a sequel called Hyperspeed that Retroism released on Steam. One of those random "let's just skip GOG" cases, I guess?
D/Generation is an old favorite of mine. Yeah, it's a sort of stealth/puzzle game with a cyberpunk theme. There's a remake on Steam that apparently sucks. Too bad.
When I was a kid I had this game called Demon's Forge, which was a graphics+text adventure. I learned years later that it was Brian Fargo's very first game; he later produced a game with a similar title (Hunted: The Demon's Forge), although it doesn't look like it has anything in common with the original.
Telarium was a company that used to make adventure games based on classic books. I had the one based on Rendezvous With Rama. I still remember the soundtrack from the intro.