Material.GetTag
GetTag(tag: string, searchFallbacks: bool, defaultValue: string = ""): string;
string GetTag(string tag, bool searchFallbacks, string defaultValue = "");
def GetTag(tag as string, searchFallbacks as bool, defaultValue as string = "") as string
Description

Get the value of material's shader tag.

If the material's shader does not define the tag, defaultValue is returned.

If searchFallbacks is true then this function will look for tag in all subshaders and all fallbacks. If seachFallbacks is false then only the currently used subshader will be queried for the tag.

Using GetTag without searching through fallbacks makes it possible to detect which subshader is currently being used: add a custom tag to each subshader with different value, and query the value at run time. For example, Unity Pro's water uses this function to detect when the shader falls back to non-reflective one, and turns off reflection camera in that case.
	// Attach this to a gameObject that has a renderer.

var materialTag = "RenderType"; function Start() { var result : String = renderer.material.GetTag(materialTag, true, "Nothing"); if (result == "Nothing") Debug.LogError(materialTag + " not found in " + renderer.material.shader.name); else Debug.Log("Tag found!, its value: " + result); }
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public string materialTag = "RenderType";
    void Start() {
        string result = renderer.material.GetTag(materialTag, true, "Nothing");
        if (result == "Nothing")
            Debug.LogError(materialTag + " not found in " + renderer.material.shader.name);
        else
            Debug.Log("Tag found!, its value: " + result);
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public materialTag as string = 'RenderType'

	def Start() as void:
		result as string = renderer.material.GetTag(materialTag, true, 'Nothing')
		if result == 'Nothing':
			Debug.LogError(((materialTag + ' not found in ') + renderer.material.shader.name))
		else:
			Debug.Log(('Tag found!, its value: ' + result))