Gosu is a programming language that is designed to be easy to use and learn, while still providing powerful features that allow developers to create robust and scalable applications. In this beginner's guide, we will provide an overview of the Gosu language, how to write it with an example, and what are the best applications for it.

Overview of Gosu:
Gosu is a general-purpose programming language that is based on Java. It is statically typed and has been designed to be both concise and easy to read, with a syntax that is similar to Java and C#. Gosu is known for its simplicity and its support for both object-oriented and functional programming paradigms.

Writing Gosu with an Example:
To write Gosu, you will first need to download and install the Gosu compiler. Once you have done that, you can start writing your first Gosu program. Here's an example of a simple Gosu program that prints "Hello, World!" to the console:

```gosu
class HelloWorld {
  static function main(args : String[]) : Void {
    print("Hello, World!")
  }
}
```

Let's take a closer look at this example. The first line declares a class called "HelloWorld". Inside this class, we have a static function called "main". This is the entry point for our program, and it takes an array of strings called "args" as its argument. Finally, we have the code that prints "Hello, World!" to the console.

Best Applications for Gosu:
Gosu is a versatile programming language that can be used for a variety of applications. Some of the best applications for Gosu include:

1. Web development: Gosu provides a number of features that make it a great choice for building web applications. It has built-in support for RESTful web services, as well as a number of popular web frameworks like Grails and Spring.

2. Insurance software: Gosu was originally created for the insurance industry, and it is still widely used in this field. Its support for business rules and domain-specific languages makes it a popular choice for creating insurance software.

3. Finance: Gosu's support for complex mathematical operations and its ability to handle large datasets make it a great choice for creating finance-related applications like trading algorithms and risk management software.

Conclusion:
Gosu is a powerful and easy-to-learn programming language that is well-suited for a variety of applications. Whether you are a beginner looking to learn programming or an experienced developer looking for a new language to try, Gosu is definitely worth checking out. In this guide, we have provided an overview of the Gosu language, how to write it with an example, and some of the best applications for it. We hope that this has been a helpful introduction to Gosu, and that you will continue to explore this exciting language on your own.