Designing for a role-playing game is equal parts science and art, and like both science and art, the blood, sweat, and tears of RPG design sometimes produces failure.
The OSR superstar contest (find your own link, I'm too lazy) is still going on (unless I've misunderstood the word "Sunday"). My own contributions are still awaiting submission (because what's the point of a deadline if you don't walk right up to it?), but they weren't the only items I came up with recently. Here are three that didn't make the cut.
Unlucky Rabbit's Foot
The owner of this item suffers a -1 penalty to her AC and saving throws, but believes the opposite.
This wax or tallow candle will not light under any circumstances whatsoever. Ever.
Armor of AC Reversal
This ornate suit of armor forces the player to use the opposite AC schematic than the one they are accustomed to. A chain mail suit of AC Reversal will be AC  to those who prefer descending AC, and AC 5 to anyone that prefers ascending AC. The degree of protection does not change, only the mechanics around it.