CheckBox in unity3d

EDIT: Try this workaround. Use a GUI Button to toggle allOptions boolean, and use GUI.Content to set an image that becomes active / inactive depending on the allOptions bool being true or false, which is toggled by the button click. Use a label to the side of the button for your On/Off text, which can have its own style like in my exmaple.

 using UnityEngine;
 using System.Collections;
 
 public class Example : MonoBehaviour 
 {
     public Texture2D texture;
     GUIContent content = new GUIContent();
     string label = "ON/OFF";
     Rect checkBoxRect;
     Rect labelRect;
     bool allOptions = true;
     GUIStyle labelStyle;
     
     void Awake()
     {
         labelStyle = new GUIStyle();
         labelStyle.fontSize = 32;
         labelStyle.normal.textColor = Color.red;
         labelStyle.fontStyle = FontStyle.Bold;
         checkBoxRect = new Rect(0, 0, 64, 64);
         labelRect = new Rect(68, 16, 128, 32);
     }
     
     void Update()
     {
         if(allOptions)
             content.image = texture;
         else
             content.image = null;
     }
     
     void OnGUI()
     {
         GUI.Label(labelRect, label, labelStyle);
         
         if(GUI.Button (checkBoxRect, content.image))
             allOptions = !allOptions;
     }
 }