Murderous Ghosts is a fun little two player story game that uses two short printout booklets and a deck of cards.
A game plays in about 15 minutes, but I usually do 3-4 in a row and alternate who plays which role (ghost or explorer).
No prep required.
Inhuman Conditions is a quick two player board game with role-playing that plays like the Voight-Kampff test in Blade Runner. I think there may be an official print and play version?