Argon or dry nitrogen are common fill gasses in high wattage bulbs. But low wattage bulbs are just vacuum with no fill.
carbon
argon
argon (Ar)
neon
neon, argon, nitrogen are all possible answers.
Tungsten is an element often found in cheaper light bulbs.
Argon is an element that is a gas at room temperature. It can be found in incandescent light bulbs because it is inert.
Argon(or nitrogen) and tungsten are used in incandescent light bulbs.
Tungsten
Tungsten
Tungsten
The bulb has a filament made up of tungsten and a low pressure inert gas (argon, neon, nitrogen).