Another great home gadget is a paper laminator... I don't carry one aboard, but virtually anything printed on paper of any value on my boat, has been laminated...
Because, well... You never know... :-)
The problem with laminators is they can destroy the legal value of a document even if they are completely readable. SSN cards are notorious for being laminated, which makes them worthless. Self authenticating documents (wills, deeds, anything notarized) also have this problem. Which is why in my legal practice I actually vacuume seal original documents like this. Easily identified, and if you need them for some reason you just cut them out of the bag. Of course living in New Orleans we have some major concerns for water damaged documents...
I don't vacuume seal my entire luggage, but there is always a t-shirt, pair of shorts, and some undies vaccume sealed in my sail bag. All three in one big bag (to keep them together), and then individually again. So no matter how much the deck hatch leaks I always know I have at least one clean dry change of clothes to put on. In fact I usually make this pack up in the beginning of the season and toss it in the bag, then forget about it until the end of the season... But when you need it it is great. Nothing like stepping off onto the deck looking presentable and clean while everyone else is wet, because you took a wave over the bow while the deck hatch was open and everyone's stuff is smoking wet.
1) spare medication
3) the boats emergency tool kit
4) a few cigars
If you can't tell I really think these are one of the best tools out there for sailors. They also open up all new storage places. Think using the bilge to store spares. Normally you wouldn't dream of it because of the water issue, but with stuff in these bags who cares... And it help take up room so the bilge pump can extract more water from the boat.