This gas is awesome to play with because it’s density alters the sound, pretty much the opposite of helium. This produces an artificially low voice as seen here on Mythbusters.
But sulfur hexafluoride is not all that fun. Since it’s less dense than air, you’ll have difficulties getting it out of your lungs. Most people have a hanging bar to suspend themselves upside down while they wait for the gas to leak out of their airway. At least the convenient part is that you’d know when the gas was gone once your voice got back to normal