Edit in JSFiddle

var myApp = angular.module('myApp', []);

myApp.filter('reverse', function () {
    return function (input, uppercase) {
        var out = "";

        for (var i = 0; i < input.length; i++) {
            out = input.charAt(i) + out;
        }

        if (uppercase) {
            out = out.toUpperCase();
        }
        return out;
    }
});

// Controller included to supply data
myApp.controller('MainCtrl', ['$scope', function ($scope) {

    $scope.greeting = 'Todd Motto';

}]);

<div ng-app="myApp">
    <div ng-controller="MainCtrl">
        <p>No filter: {{ greeting }}</p>
        <p>Reverse: {{ greeting | reverse }}</p>
    </div>
</div>