ItemEntityCatcher
public abstract class ItemEntityCatcher extends Item {

    public ItemEntityCatcher(String name) {
        setMaxStackSize(1);
        setUnlocalizedName(EntityCatcher.MODID + "_" + name);
        setCreativeTab(EntityCatcher.tab);
        setRegistryName(name);
        GameRegistry.register(this);
    }

    @Override
    public EnumActionResult onItemUse(ItemStack stack, EntityPlayer player, World world, BlockPos pos, EnumHand hand, EnumFacing facing, float hitX, float hitY, float hitZ) {
        if (!world.isRemote) {
            NBTTagCompound nbt = NBTTagCompounds.getOrCreateTag(stack);
            NBTTagCompound entityNBT = nbt.getCompoundTag("WrittenEntity");
            Entity entityFromNBT = EntityList.createEntityFromNBT(entityNBT, world);
            world.spawnEntityInWorld(entityFromNBT);
            stack.damageItem(1, player);
        }
        return EnumActionResult.SUCCESS;
    }

    @Override
    public void addInformation(ItemStack stack, EntityPlayer playerIn, List<String> tooltip, boolean advanced) {
        super.addInformation(stack, playerIn, tooltip, advanced);
    }

    public static class SingleUseEntityCatcher extends ItemEntityCatcher {

        public SingleUseEntityCatcher() {
            super("single_use_catcher");
            setMaxDamage(1);
        }
    }

    public static class MultiUseEntityCatcher extends ItemEntityCatcher {

        public MultiUseEntityCatcher() {
            super("multi_use_catcher");
            setMaxDamage(25);
        }
    }
}


The Event Handler:
public class ECEventHandler {

    @SubscribeEvent
    public void interactionEvent(PlayerInteractEvent.EntityInteract event) {
        EntityPlayer player = event.getEntityPlayer();
        if (!player.worldObj.isRemote) {
            Entity entity = event.getTarget();
            if (entity != null && !entity.isRiding()) {
                ItemStack held = player.getHeldItemMainhand();
                if (held != null && held.getItem() instanceof ItemEntityCatcher) {
                    NBTTagCompound nbt = NBTTagCompounds.getOrCreateTag(held);
                    NBTTagCompound entityNBT = new NBTTagCompound();
                    entity.writeToNBTOptional(entityNBT);
                    nbt.setTag("WrittenEntity", entityNBT);
                    entity.setGlowing(true);
                    entity.attackEntityFrom(EntityDamageSource.outOfWorld, Float.MAX_VALUE);
                }
            }
        }
    }
}