I don't know if this qualifies as an unknown or unremembered game (more likely unremembered), but Star Wars Jedi Knight II: Jedi Outcast was a pretty meaningful game for me as an aspiring gamer. I got that game with my brother (first video game we ever purchased) more than a decade ago, and it has stuck with me ever since. I don't think we quite knew what we were getting into at first. The difficulty was insane, especially for a couple of kids essentially brand new to gaming. But we fought through to the end, and I loved every bit of it. Going back to the game years later, (on the hardest difficulty setting, mind you) my memories of the game as being difficult were reinforced. Especially the first levels where you don't have a lightsaber, you're in a constant struggle for survival. As you progress, you slowly become more and more powerful, until you're using force lightning to blast large groups of stormtroopers off ledges and having elegant saber duels with hardened dark Jedi. It never got easy, but the pacing of the increase in skill and the wonderful difficulty curve is something I don't think I've ever seen done as well in another game, and it's a shame most games these days seem intent on throwing a constant stream of upgrades and perks on you to bait you along, instead of crafting a challenging experience that doesn't need RPG-esque leveling to still make you feel like you're improving. I can hardly say enough about how good the game was. There was so much nuance in the lightsaber fighting, levels were (mostly) well designed (surprising, occasionally!) and good at throwing challenges at you. And the mid-game boss fight with an agile lightsaber wielding opponent still stands among my favorite gaming moments. Jedi Knight II was a brilliant game, and I'm happy that by some stroke of luck I stumbled upon it.