Not actually C++, it's SourcePawn.

buildmode.cpp

//http://code.google.com/p/ihackedgmod/
//http://creativecommons.org/licenses/by-sa/3.0/
#include <sourcemod>
#include <sdktools>
#include <colors>

public Plugin:myinfo =
{
  name = "Build Mode",
	author = "nicatronTg",
	description = "Plugin by nicatronTg(Shank)",
	version = "0.0",
	url = "http://twitter.com/nicatronTg"
}

public OnPluginStart()
{
	CreateTimer(15.0, LoadStuff)
	HookEvent("player_hurt", event_PlayerHurt, EventHookMode_Pre);
	RegConsoleCmd("say", ConsoleParse)
}

public Action:event_PlayerHurt(Handle:event, const String:name[], bool:dontBroadcast) {
	new client = GetClientOfUserId(GetEventInt(event, "attacker"));
	
	if (
		client &&							// Not world/self
		GetEntityFlags(client) & FL_GODMODE	// attacker is in god-mode
	) {
		client = GetClientOfUserId(GetEventInt(event, "userid"));
		
		SetEntProp(client, Prop_Send, "m_iHealth", GetClientHealth(client) + RoundToCeil(GetEventFloat(event, "damage")));	// Restore health
		SetEventFloat(event, "damage", 0.0);	// Remove damage for other plugins
	}
	
	return Plugin_Continue;
}

public Action:LoadStuff(Handle:timer)
{
	/*Insert all pre-run code here.*/
	AutoExecConfig(true, "build_config")
	CPrintToChatAll("{green}[Build Mode] {default}Protected by Build Mode.")
	CPrintToChatAll("{green}[Build Mode] {default}Created by nicatronTg")
	CPrintToChatAll("{green}[Build Mode] {default}Released under Creative Commons 3.0 Share Alike Unported")
	CPrintToChatAll("{green}[Build Mode] {default}http://code.google.com/p/ihackedgmod/")
	return Plugin_Handled;
	//Removing this portion violates the copyright placed upon this code.
	//Making this section un-reachable in any means will also violate the CC 3.0 BY-SA.
	//Any attempt to remove it will result in a case in the state of Colorado Arapahoe County Court sytems
	//I ain't fucking with you, you can read.
}

public Action:ConsoleParse(client, args)
{
	/*Snippet from http://wiki.alliedmods.net/Commands_%28SourceMod_Scripting%29*/
	new String:text[192];
	GetCmdArgString(text, sizeof(text));

	new startidx = 0;
	if (text[0] == '"')
	{
		startidx = 1
		/* Strip the ending quote, if there is one */
		new len = strlen(text);
		if (text[len-1] == '"')
		{
			text[len-1] = '\0'
		}
	} //Why re-create the wheel? Just steal from a pre-built snippet
	
	if(StrEqual(text[startidx], "!build"))
	{
		CPrintToChatAll("{green}[Build]{default} %t has entered build mode. Killing them via alternate means will result in a permanent ban.", client)
		CPrintToChat(client, "{green}[Build]{default} Change your name so that it begins with (NoKill)")
		GodMe(client, true)
		return Plugin_Continue;
	}
	else if(StrEqual(text[startidx], "!dm"))
	{
		CPrintToChatAll("{green}[Build]{default} %t Doesn't like people, so he's coming after you.", client)
		CPrintToChat(client, "{green}[Build]{default} Change your name back from (NoKill). You aren't invulnerable.")
		GodMe(client, false)
		return Plugin_Continue;
	}
	return Plugin_Continue;
}

bool:GodMe(const any:client, const bool:mode) {
	new fFlags = GetEntProp(client, Prop_Data, "m_fFlags");
	
	if (mode) {						// Wants nokill mode
		if (fFlags & FL_GODMODE) {	// Already god-moded
			return false;
		} else {					// Not a god.
			fFlags += FL_GODMODE;	// Add god-flag
		}
	} else {						// Wants to be killable.
		if (fFlags & FL_GODMODE) {	// Currently god-moded.
			fFlags -= FL_GODMODE;	// Add god-flag
		} else {					// Already killable
			return false;
		}
	}
	
	SetEntProp(client, Prop_Data, "m_fFlags", fFlags);	// Set new flags
	return true;
}