Natural products have various applications.
1) Drugs and Drug leads.
2) Cosmetic and Perfume industry.
3) Paints and Varnishes.
4) As foods.
5) In defence( military).
6) For pest control.
A natural product is usually considered as a pure chemical. However, even the raw materials from which they are obtained are considered natural products by some schools.
The important applications are elaborated below.

1) Drugs and Drug leads:-
This is a familiar field as far as pharmacy is concerned. Quinine was first used for malaria and later quines were developed. Thus, quinine is both a drug and drug lead, same is the case with vinicristin and viniblastin for a number of years. They were used as such to treat cancers, mainly lukemia before semi-synthetic derivatives were prepared. The latest example of natural products acting as drug leads is the venum of a viper. Based on the structure of a peptide isolated from this, majority of the "prils"(Enalapril) were developed. This is to emphasize the importance of natural products as drugs and drug leads in short.

2) In cosmetics and perfumes:-
All the materials used in perfumes and majority of the chemicals used in cosmetics are of natural origin. The volatile oils used in these are of natural origin. Though it is a multi billion dollar industry the importance of natural products un-noticed. Even the fixatives use are of natural origin.

3) In Defence:-
Though there is no evidence to sight, I believe that natural products can play a great role in defence, war-fare, rockets etc. While some can act by causing allergy, some can help ignition processes. Some can even have propellant action. It is possible that some can modulate the burning materials. Rockets of Diwali were being manufactured in India much before the Space technology development. This is the basis for the above mentioned hypothetical uses.

4)As Pesticides:-
The most famous example is Azadirachtin, the source of which is the neem tree. Bio-pesticides have caught up the attention of the whole world after this discovery.