Unity Decal Shader

Shader "Example/Decal"
{
	Properties
	{
		_MainTex("Base (RGB)", 2D) = "white" {}
	}
		SubShader
	{
		Tags{ "RenderType" = "Opaque" "Queue" = "Geometry+1" "ForceNoShadowCasting" = "True" }
		LOD 200
		Offset -1, -1

		CGPROGRAM
#pragma surface surf Lambert decal:blend

		sampler2D _MainTex;

	struct Input
	{
		float2 uv_MainTex;
	};

	void surf(Input IN, inout SurfaceOutput o)
	{
		half4 c = tex2D(_MainTex, IN.uv_MainTex);
		o.Albedo = c.rgb;
		o.Alpha = c.a;
	}

	ENDCG
	}

Fallback "Diffuse"
}

Decal

Decal are commonly used to add details to materials at runtime (bullets impacts are for example). They are a great tool especially in deferred rendering as they alter the GBuffer before it is lit, thus saving on performance.

In a typical scenario Decal should probably be rendered after the opaque objects and should not be a shadow caster as seen in the shaderlab “Tags” in the example below.
-Split82

I fixed the errors that were present in the original code (line ending issues and rogue space inbetween - and 1 for the offset).
Changed brackets to better suit my coding style of choice and added a Fallback for Diffuse.