A basketball sized can that can diffuse up to a typical lightning bolt's worth of energy into gamma rays. In 100 words.
This ever-full, ever-surprising, ever-ridiculous flask contains a magical liquid that may be the best or worst thing you've ever drank. Handling with caution won't do you any good.
100 word magic item
The King always has the coolest form of transportation.
Combating any monster is often as simple as having the right tool for the job. The nightmarish lycanthrop is no exception.
These relatively plain silver rings allow the wearer to go unseen, unheard, and un-smelled and render the wearer completely intangible - but only to others who wear a Ring of Mutual Exclusion.
A longsword that lashes out in the hands of a graceful warrior.
The two gently-humming, crystal-studded blades are semi-transparent and sharpened to a deadly razor edge. The haft between the blades is decorated with brilliant multi-colored crystals. The balance and craftsmanship are perfect. You feel that these trusty blades will never fail you.
With regard to the plot "Sleeping Mines of Elathon":
You manage to get the water wheel in the mine working which operates a pump to clear the flooded lower levels. As you explore the dank tunnels of the lower galleries, you can hear the creaking of the wheel above. You enter a low-ceilinged passage and are crawling on your backs, when the creaking stops. The water starts seeping wetly around the back of your head...