If I did not have the PLB, I feel like I should say the next item would be a knife, but the truth is that fire is so important for warmth, mental health, and signal that I think I'd have to say #1 Good Lighter or sparker & tinder, and then #2 Knife. #3 would be that bright shelter material I mentioned above.
My thinking on the knife versus lighter issue was that I can start a fire with a knife (bow method or fire plow) but I'd have a hard time cutting something with a lighter.