If you have a fort under siege, then you can also give any command a Black Heart (not just stealthy ones) and you are then able to issue then the assassinate command.
This only has niche usage though, but could be very useful for taking out key commanders just before a siege attempt. Especially ones resilient to Earth Attack. The commander can assassinate and take part in a siege defence in the same turn. Tart assassins anyone?
Although this could easily be considered as too gamey, or even just a basic exploit. But it happens too rarely for it to be brought up for attention.