Menu Bar

You can put your own entries in the unity menu bar. Some paths have special meaning though, like the Assets/Create/ path, where items in that path are also displayed in the Create section of the hierarchy view context menu.

Menu item example

using UnityEngine;
using UnityEditor;

public static class MyMenuFunctionality
{
    [MenuItem("Assets/Create/Funny GameObject")]
    private static void CreateFunnyGameObject()
    {
        var gameObject = new GameObject("I'm fun.");
        gameObject.transform.position = Vector3.zero;
    }
}