Halon 1301 is still used for fire suppression aboard ships and aircraft. It can be safely flooded into confined spaces without killing people.
Calling these agents "oxygen suppressing" is a HUGE misnomer. Halon, FM200, etc don't work by reacting with the oxygen in the room. Although displacing some oxygen contributes to their method of action, this isn't the primary way they put out fires.
Halon and friends stop fires by catalytically interrupting gaseous fire reaction products. As it was explained to me, these reactions can be counterintuitive - eg, the production of reduced hydrogen gas (H2) from free radicals. You wouldn't expect Halon to put out a fire by making hydrogen, but it does.
