I was looking through my books, and saw the Horizon Walker's Shifting Planar Terrain Mastery, obtainable upon reaching Horizon Walker 6, which gives Dimension Door every 1d4 rounds at a caster level equal to your class level. I thought this could make for a very cool teleporting assassin, And I've been trying to come up with the best way to implement it. Horizon Walker is clearly designed with ranger in mind as the entry class, or druid, but I think it's probably doable with plenty of other classes, most obviously Scout. I think sneak attack would be better for this build than skirmish, but the Knowledge (geography) requirement puts back entry into Horizon Walker by several levels. Also, I'm not really sure how to end the build after 6 levels of HW.
TL;DR: Horizon Walker as a basis for a teleporting assassin-type character, any ideas?