Dungeon Crawl Stone Soup is an open-source, single-player, role-playing roguelike game of exploration and treasure-hunting in dungeons filled with dangerous and unfriendly monsters in a quest to rescue the mystifyingly fabulous Orb of Zot.
I’m a sucker for for retro games and Dungeon Crawl Stone Soup looks like a solid roguelike. It can also be played online via SSH and it’s open-source to boot. Win-win-win.