Configuration Settings Source Model for Product Attribute Collection

Attribute.php

<?php
/**
 *
 * @category    Webdawe
 * @package     Webdawe_General
 * @author      Anil Paul
 * @copyright   Copyright (c) 2016 Anil Paul
 * @license
 */
class Webdawe_General_Model_System_Config_Source_Product_Attribute
{
    /**
     * Retireve option Array of Product Attributes
     * @return array
     */
    public function toOptionArray()
    {
        $collection = Mage::getResourceModel('eav/entity_attribute_collection')
            ->setEntityTypeFilter(Mage::getModel('eav/entity')->setType('catalog_product')->getTypeId())
            //->addFieldToFilter('backend_type', 'int'); // Uncomment if you want to filter with backend type
        $cols = array();
        foreach($collection->getItems() as $col)
        {
            $cols[] = array('value' => $col->getAttributeCode(),   'label' => $col->getFrontendLabel());
        }
        return $cols;
    }
}