Secrets & Shadows and Starfarer are two skins to the same game. The former is paranormal romance, or urban fantasy, if you prefer, while the latter is straight science fiction. Draws heavily on Lady Blackbird for character generation and Apocalypse World for resolution and mechanics.
No built-in structure or end point, but plenty of color and situation starters to get things going and keep them moving. Should be playable solo or in a group, one shot or long term.
I expected to make a lot of these in different flavors, but ended up refining the system and condensing it, along with six or seven other scenarios, into The Calypso Compendium.