<select ng-model="productSelected" ng-options="rsProduct.price for rsProduct in lsProduct" ng-change="changeProduct()" data-valid="required"> <option value="" ng-selected="selected">Seleccione ...</option> </select>
Otro
<select ng-init="productSelected=''" ng-model="productSelected" ng-options="rsProduct.price for rsProduct in lsProduct" ng-change="changeProduct()" data-valid="required"> <option value="0" ng-selected="selected">Seleccione ...</option> </select>