The Dreamcast port of Half-Life 1 was meant to be released some time in 2000, but never made it to retail, mostly because Sierra realized the Dreamcast wasn’t gonna stick around too long, and that releasing the port would be a waste of time and money.
It was leaked to the internet, and surprisingly, the port has quite a community behind it! Quite a few mods have been ported to the Dreamcast: Opposing Force, the classic They Hunger, CS: Condition Zero: Deleted Scenes, even Counter-Strike, and now, Paranoia!
This port was created by just two people! Remember, it’s a homebrew port for a leaked, unfinished 2000 Dreamcast port, so don’t go in expecting Dear Esther. You don’t actually require HL1 on the Dreamcast, but it does apparently use its data. So, if you’ve got a Dreamcast lying around, why not check this out?