I think I would opt for a short spear of some kind or some other thrusting, piercing weapon like a fencing foil which could be used in close quarters. A sword would be nice but swinging it around in a hallway or some other confined area just seems impractical. A bow or crossbow might be sufficient but keep in mind, if there were more than one BG, you would have to take a few seconds to reload, draw and fire.
Interesting and thought provoking question.
Interesting and thought provoking question.