I've got a good one today, the Chzo Mythos series. They're a horror adventure game series, and they're really good.
PLAY THEM IN ORDER!!!
5 Days a Stranger-A haunted house tale begins the saga. In many ways, it's the best of the bunch.
7 Days a Skeptic-A starship crew faces a supernatural threat (hint hint, it's a sequal)
WARNING: The Following games completely 360 the plot of the first two games. Trilby's notes is awesome, but the ending is a lead for the next game. I thought the ending of the series got kind of Evaesque, so be warned.
Trilby's Notes-Trilby, the protagonist of the first game, finds himself in a hotel on the trail of the menace from the other games in the series.
6 Days a Sacrifice-This one 'Ties up the lose ends' of the other games in the series. It's easily the weakest, but you
will want to finish it if you played Trilby's Notes.
This sword calls me it's master, but I feel more like it's slave.