My vote would be scrolls of teleportation. You can't keep them handy, otherwise they risk burning up. So in order to actually use one you have to a) take it out of your chest and b) read it, which takes some time too. When you do need one urgently, those 2 steps are costly, and in my experience you're dead before you even finish reading
To lay them outside the sumo's house, then place a banana behind them to tempt him. He will keep walking over them, weakening him, making him easier to defeat