Add Custom Block in Cart Page Above Coupon Block – Magento 1.9

I guess it depends on what your trying to add and if it needs to be at a particular point e.g before or after the add to cart button.

If after the addtocart button is ok you can use product.info.addtocart since it calls <?php echo $this->getChildHtml('', true, true) ?>.

e.g

<catalog_product_view>
    <reference name="product.info.addtocart">
        <block type="core/text" name="core-text"><action method="setText"><text><![CDATA[<div>Test</div>]]></text></action></block>
    </reference>
</catalog_product_view>

Update: If you wrap the text in a div as I have updated above it will work in the default theme like below. But this may not work quite right in other themes like the new rwd.

In the class Mage_SalesRule_Model_Quote_Discount there is this method that adds the discount total to the list of totals:

public function fetch(Mage_Sales_Model_Quote_Address $address)
{
    $amount = $address->getDiscountAmount();

    if ($amount!=0) {
        $description = $address->getDiscountDescription();
        if (strlen($description)) {
            $title = Mage::helper('sales')->__('Discount (%s)', $description);
        } else {
            $title = Mage::helper('sales')->__('Discount');
        }
        $address->addTotal(array(
            'code'  => $this->getCode(),
            'title' => $title,
            'value' => $amount
        ));
    }
    return $this;
}

You can see here that the total is added only when the discount amount is not zero if ($amount!=0) {.
So just rewrite this class and change the method I mentioned. Remove the if statement and it should work.