Helium: It is used for filling balloons and deep diving. It can also be used as gas tungsten arc welding.
Neon: It is mainly used in neon signs for illumination. It can be used in vacuum tubes, high-voltage indicators, television tubes, and so on.
Argon: It is often used for filling incandescent lights. For semi-conductor industries, the crystals are produced in argon gas, it is inert to prevent the crystals from oxidiziong by air.
Krypton: It sometimes mixed with argon as the fill gas of energy saving fluorescent lamps. The main use of krypton is the photographic flashes.
Xenon: Some photographic flashes and stroboscopic lamps are filled with xenon as the flash lamps. It is also used in some lamps and nuclear reator.
Radon: It is always used in radiotherapy. For scientific uses, radon can be used to track air mass to a limited degree.