With XMLSpear you can open an XML document and matching schema. You will be presented with a graphical interface based on the particular document and schema. All your updates will be validated against the schema. Mac OS users can open and edit their plist files, even when they are in binary format.
XMLSpear is packaged with a MQSeries plugin for browing queues and putting messages, so you can even test your MQ based services.
Requires Java Runtime Environment. Get It Here.