key-value pairs in ng-options

use ng-option:

<select ng-model="blah" ng-options="key as value for (key , value) in data"></select>

or use ng-repeat:

<select>
    <option ng-repeat="(key, value) in data" value="{{key}}">{{value}}</option>
</select>

data in controller:

$scope.data = {
    "key1": "val1",
    "key2": "val2",
    "key3": "val3",
    ...
};