Not thunking tooo hard about this ..its late and i should be tucked up in bed !!
Portable Hole... excellent bit of kit ! Never leave the home without it !
of course its stuffed with all those indispensable thingymajigs every adventurer needs..like a ball of string, some chalk, a bag of caltrops and a ladder.
Game mechanic wise...I'd have to go with Healing potions. Help keep the game alive by keeping the characters alive.. got to be good!