MonoBehaviour.OnDrawGizmos()
Description

Implement OnDrawGizmos if you want to draw gizmos that are also pickable and always drawn.

This allows you to quickly pick important objects in your scene.

Note that OnDrawGizmos will use a mouse position that is relative to the Scene View.

This function does not get called if the component is collapsed in the inspector.
	function OnDrawGizmos() {
		// Draw a yellow sphere at the transform's position
		Gizmos.color = Color.yellow;
		Gizmos.DrawSphere (transform.position, 1);
	}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnDrawGizmos() {
        Gizmos.color = Color.yellow;
        Gizmos.DrawSphere(transform.position, 1);
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnDrawGizmos() as void:
		Gizmos.color = Color.yellow
		Gizmos.DrawSphere(transform.position, 1)