How do I remove unwanted Transform Orientations? I'm using a lot of custom-defined transform orientations (Ctrl+Alt+Space) recently while modeling. The list has grown too large, how do I remove some or all of them?
The custom transforms are also listed in the 'Transform Orientations' panel in the Properties shelf (N).

Choose the custom transform you would like to delete from the list, then press the 'x' next to it to remove it: