Dinitrogen oxide is a sweet-smelling gas used as an anesthetic. It is sometines called "laughing gas" because it makes some people laugh before and after they are unconscious. Demonstrations of laughing gas were made in 19th century in private houses in London, England for fun. Scientists later realized how useful it could be as an anesthetic.
Nitrogen is unreactive, so it is used to keep oxygen--a very reactive gas--out of many containers. For example, ethanol is likely to catch fire if it comes in contact with oxygen, so nitrogen is pumped into the ethanol storage tanks. Another example is potato chip bags. Filling them with nitrogen keeps oxygen from reacting with the fat and making them go stale.
Many people put nitrogen fertilizers in their gardens to replace the nitrogen the plants remove. Previously, manure was used, but today many people use synthetic fertilizers like nitrates and ammonium sulphite.
Liquid nitrogen is used to quick-freeze food. The food is first cooled by nitrogen gas, then sprayed by liquid nitrogen.
Most chemical explosives contain nitrogen. These include nitroglycerin and trinitrotoluene (TNT). Nitroglycerin is an unstable, oily liquid that is made safer by being mixed with clay to make dynamite.