Casts a ray through the scene and returns all hits. Note that order is not guaranteed.

	function Update () {
		var hits : RaycastHit[];
		hits = Physics.RaycastAll (transform.position, transform.forward, 100.0);
		// Change the material of all hit colliders
		// to use a transparent Shader
		for (var i = 0;i < hits.Length; i++) {
			var hit : RaycastHit = hits[i];
			var renderer =  hit.collider.renderer;
			if (renderer) {
				renderer.material.shader = Shader.Find("Transparent/Diffuse");
				renderer.material.color.a = 0.3;
			}
		}
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Update() {
        RaycastHit[] hits;
        hits = Physics.RaycastAll(transform.position, transform.forward, 100.0F);
        int i = 0;
        while (i < hits.Length) {
            RaycastHit hit = hits[i];
            Renderer renderer = hit.collider.renderer;
            if (renderer) {
                renderer.material.shader = Shader.Find("Transparent/Diffuse");
                renderer.material.color.a = 0.3F;
            }
            i++;
        }
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Update() as void:
		hits as (RaycastHit)
		hits = Physics.RaycastAll(transform.position, transform.forward, 100.0F)
		i as int = 0
		while i < hits.Length:
			hit as RaycastHit = hits[i]
			renderer as Renderer = hit.collider.renderer
			if renderer:
				renderer.material.shader = Shader.Find('Transparent/Diffuse')
				renderer.material.color.a = 0.3F
			i++

Notes: This function will return false if you cast a ray from inside a sphere to the outside; this in an intended behaviour. If you move colliders from scripting or by animation, there needs to be at least one FixedUpdate executed so that the physics library can update it's data structures, before a Raycast will hit the collider at it's new position.