Main:

package mc.zombieapocalypse;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import mc.zombieapocalypse.common.blocks.BlockBunkerMetal;
import mc.zombieapocalypse.common.core.ZACommonProxy;
import cpw.mods.fml.common.Mod;
import cpw.mods.fml.common.Mod.Instance;
import cpw.mods.fml.common.SidedProxy;
import cpw.mods.fml.common.event.FMLPreInitializationEvent;
import cpw.mods.fml.common.network.NetworkMod;
import cpw.mods.fml.common.network.NetworkMod.SidedPacketHandler;
import cpw.mods.fml.common.network.NetworkRegistry;

@NetworkMod(clientSideRequired = true, serverSideRequired = true,
clientPacketHandlerSpec = @SidedPacketHandler(channels = {"ZombieApocalypse"}, packetHandler = ClientPacketHandler.class),
serverPacketHandlerSpec = @SidedPacketHandler(channels = {}, packetHandler = ServerPacketHandler.class))

@Mod(modid = "marcosza", name = "Zombie Apocalypse", version = "0.0.1")
public class ZAMain{
	@Instance("marcosza")
	public static  ZAMain instance = new ZAMain();

	@SidedProxy(clientSide = "mc.zombieapocalypse.client.core.ZAClientProxy", serverSide = "mc.zombieapocalypse.common.core.ZACommonProxy")
	public static ZACommonProxy proxy;

	public static Block BunkerMetal;

	@cpw.mods.fml.common.Mod.PreInit
	public void PreInit(FMLPreInitializationEvent event){
		BunkerMetal = new BlockBunkerMetal(2012, Material.iron).setUnlocalizedName("Bunker Metal");
	}
	@cpw.mods.fml.common.Mod.Init
	public void Init(FMLPreInitializationEvent event){
		proxy.registerBlocks();
		proxy.registerItems();
		NetworkRegistry.instance().registerGuiHandler(this, proxy);
	}
}

Block:

package mc.zombieapocalypse.common.blocks;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import net.minecraft.client.renderer.texture.IconRegister;
import net.minecraft.creativetab.CreativeTabs;

public class BlockBunkerMetal extends Block{

	public BlockBunkerMetal(int par1, Material par2Material) {
		super(par1, par2Material);
		setHardness(4.0f);
		setResistance(5.0f);
		setCreativeTab(CreativeTabs.tabBlock);
	}
	public void registerIcon(IconRegister par1iconregister){
		this.blockIcon = par1iconregister.registerIcon("ZombieApocalypse:BunkerMetal");
	}
}