My favorite low-lethality weapon is actually a spell. Petrify (and spells based off it) offers a quick way to drop someone out of a fight and keep them there until you stop concentrating. Get a cart and some ID as an artist, and you can even move someone through the sprawl in broad daylight, claiming that it is an art piece and you're taking it to a client.
Of course, the permanent version I made back in 4e is also 'technically' nonlethal, in that the person never died, but it did make for an excellent assassination tool.