Oh Grim Fandango, how I love thee. This game didn't get anywhere close to the attention is deserved. The music, the environments, the characters, the plot, all of it is just so beautifully done, and comes together better than a bukkake party. I've completed it many a time over the years, and it never gets dull.
I recently managed to acquire the soundtrack, and dear God, it is great.
Also, the Mexican folklore elements are brilliantly done, and placed within the game ingeniously. Lucasarts' finest moment? I think so.