Just for kicks, Gossen's Ultra-Spot is rated down to 1EV. I've never owned/used it. There was a time I wanted one bad. Now I have enough. Still it might be most sensitive spot meter.
There were two film cameras that had extremely sensitive built in meters, the Canon A1 and the Leica M6 TTL. Both meters had a range extending down to EV -2. I kept an A1 around for years, just to use it as a light meter for very dark situations.