It's widely understood, in the collective consciousness of the meme-anschauung, that inhaling sulphur hexafluoride is how one briefly attains an extremely deep and manly voice. But there is a gas that offers even deeper and manlier formants: perfluorobutane. Cody's lab:
"I breath in samples of sulfur hexafluoride and perfluorobutane which has nearly twice the density. I plan to do a longer more detailed video eventually."
If you missed the first season of Star Trek: Discovery and are curious about what went on with the Klingons, this video basically gets you up to speed.