public class Rssting : MonoBehaviour {

    private void OnDrawGizmosSelected()
    {
        Gizmos.color = Color.red;
        Gizmos.DrawLine(transform.position, transform.TransformPoint(transform.up * 5));
        Gizmos.DrawCube(transform.position, Vector3.one * 2);
    }

    private void OnDrawGizmos()
    {
        Gizmos.DrawSphere(transform.position, 1);
    }
}

OnDrawGizmosSelected会在物体选中时执行，绘制辅助元素。OnDrawGizmos会在所有拥有这个脚本组件的物体上绘制辅助元素，不需要被选中。