Custom DrawGizmos for scripts attached to gameobjects in Editor

DrawGizmos.cs

using UnityEngine;
using UnityEditor;

public class DrawGizmos
{
    [DrawGizmo(GizmoType.Active)] // there are also other options for gizmotypes
    static void DrawMyGizmo(MyScript script, GizmoType gizmoType) // set MyScript as your script class/name
    {
        Debug.DrawRay(script.transform.position, script.transform.up*10, Color.red);
    }
}