Something like Oxygen XML or XMLSpy editors Grid View for JSON/XML files. It's very handy when dealing with complex documents that have several levels of nested Arrays or embedded documents.
Currently in MongoChef if you are in a collection root level with table view and "dive in" a nested element you lose the original context so if you want to look into another document's nested element you have to go back one level up and then lose the first bit of data you were looking at...

You can use the tree view but the data is laid out vertically so you quickly run out of space and the fields are not nicely aligned in columns. A grid view kind of mixes table and tree views.