How about an Everburning Torch that
is hot enough to set things on fire, and
does consume oxygen? You wouldn't want to put it in your backpack, that's for sure!
Torm said:
Ring of Sleep - when activated by the wearer, causes wearer to take a nap.
Actually, I could see some players abusing the hell out of this item.
Player: "I'm out of spells; let's rest for 8 hours."
DM: "You just woke up an hour ago. There's no way you could fall asleep now."
Player: "Then I'll use my Ring of Sleep."
Better make it a Ring of Restless Sleep. They fall asleep, but do not recover from fatigue or regain spells, and can be woken by the slightest disturbance (so you can't even trick someone into using it and then coup-de-grace them).
Actually, though, a lot of these items sound really nice for flavor. I've been planning a low-magic campaign for a while now; maybe these are the sort of things I'll have for sale in 'magick shoppes'. Little more than curiosities, but very useful to a clever PC under the right circumstances.