At one point in the development of EQ:CON we needed an item to test out a quest. The guy doing our plotline hadn't gotten this far, so we were just going to stuff something random in there temporarily for coding purposes.
I suggested naming it the Item of Infinite Value.
It turned out that the plot, as we knew it then (I don't know if this was kept or not) involved a ship owner that you needed to buy a ship from. He was going to send you on a quest to fetch some object for him - and yes, this is the quest we were working on - but it had always jarred a bit. Why couldn't you just give him a lot of money and move on? Why make it a quest?
So we immediately had the mental image of the following conversation.
"Hello, is this boat for sale?"
"Yes, it is! I'm selling it for the low low price of AN INFINITE AMOUNT OF MONEY."
"Here you go."
"Why thank you! The boat's yours."
Even better, we realized, there was no reason you should just give him the item. You should have to go sell it at a shop first! And the shopkeeper would give you an infinite amount of money.
"Current gold: Infinity plus 17,328 gold pieces."
Which immediately brings up a few other questions (what happens if you spend more than the 17,328? "Sorry, I don't have change for infinity." Where are you carrying it - is there a coin that says "infinity" on it? If it's countably infinite, can't you duplicate it?) but we felt these were solvable problems.
Somehow it never got into the game, though.
Can't imagine why.