I don't think you need caps to get ghosts from sign. "Give me a sign" is something people have said to ghosts for a long time. That's where the movie GOT the word.
To me Washington and server are best for signature signing.
The "give me a sign" thing is more to heavens and prayer type stuff idk, never made me think of ghosts - and to assume spymaster wants that entire phrase is already a stretch imo. Anyway, I obv dislike ghost no reason for me to rip on it more
I'd rather ghost or disease, but I guess we're at Washington or Server or Tablet for consensus.
Those are the only 5 I would consider here. I guess Tablet would be my favorite of the latter 3 (because you can sign a receipt on a tablet), but it's close.
I still don't like ship, and missile and jet somehow make even less sense to me.