A couple of other cases:
11. To clear the hand in case of mandatory golem actions. E.g. I have nobles, golem & a curse in hand and a remake in the deck. I might get two useless actions out of nobles in order to be safe from the mandatory trash.
12. Mostly contrived, but I could see playing something like vault (with nothing left to draw or wish to discard) in order to induce your opponent to discard garbage so you have better odds of getting a better card from masquerade.
13. Likewise, I could in theory see playing a dead council room or other opponent aiding card (vault, dead hags with horse traders in play, etc.) to help the next player buy the last province instead of the guy after him to seal my victory. E.g. I have 4 provinces & a duchy, next player has 3 provinces, and last guy has 3 provinces & 2 duchies, then I'll play a dead council room hoping that the next player hits 8 coin and ends the game.
14. I could see playing a dead council room to muck with an opponent's reshuffles. E.g. I have a hand of council room, gold, gold, minion, nothing else playable (discard or deck), and + coin from earlier fishing villages. My opponent meanwhile has a lot of good cards in hand with all his green in the discard, and nothing in the draw deck. I might drop the council room to trigger his reshuffle and then minion him to make his power cards miss the shuffle.
15. Very contrived, I could see playing governor even when golds are exhausted in order to either slow down hot decks with silver or to provide treasure feed for pirate ships (maybe the opponents are running really small TR/Remodel decks?).