Nitrogen filled tyres:
Nitrogen has been used for decades in the tyres of aeroplanes, as well as in motorsport. Nitrogen is an insert gas and remains in the gaseous state at very low temperatures and so it doesn't liquefy at high altitude where temperatures range close to -40 degrees. Since nitrogen doesn't freeze at those temperatures, it doesn't cause any issues when an aircraft lands.

Now, even some passenger cars use nitrogen to inflate their tyres. Nitrogen is used because:

The outer section of the tyres have steel , so using compressed air isn't much of a problem as the amount of moisture in contact with the metal is minimal. Pressure loss is reduced with usage of nitrogen.

Nitrogen should be used only for certain applications, it isn't worth the trouble and money to use nitrogen in normal passenger cars.

When the tyre rolls, the sealant is spread uniformly on the inside surface of the tyre. If a nail punctures the tyre, then it pierces through the tread to this inside surface. The air pressure forces the sealant to close the opening. Thus, the tyre opening is sealed within a couple of rotations of the tyre and the driver doesn't realize about the incident. When the nail is inspected and removed, the sealant is capable of sealing the tyre again, usually without any loss of pressure.

Alloy Wheels:
Most passenger cars come equipped with steel rims. These rims are heavy and hence increase the weight of the wheel-tyre combination. Alloy wheels are lighter and look better than regular rims and wheelcaps, making your car look more attractive.

Before buying alloy wheels, find out what their maintenance costs are and the problems they face. Studies have shown that alloys have a greater inclination to undergo corrosion resulting in the leakage of air. The one advantage that the alloys have is that they can be repaired regardless of the damage.