My code phrase is "just a minute" -- a phrase I developed a habit for when people want to interrupt me at work when I'm not in a place where I can safely pause.
Even if I'm doing something so simple as writing out a label (we just packed up to move, so its fresh on my mind) and my GF says something to me, I won't respond until I get done writing it out. She gives me shit and says I can't multitask, but dammit let me focus.