Which Airline don't use the Flight Number 191 anymore because of bad luck?
Well, you can be pretty sure that Delta and American no longer use that flight number, as it is pretty standard for airline to retire a flight number of an accident flight.

Beyond that, I'm sure there are a multitude of carriers still using Flight 191.

For example, Air India 191 is in-flight at the time of writing . Air Canada 191 is scheduled