oddly enough i have a cast iron d20

Hmmm... I wonder if, with a little work, I could make a wooden D20 and put a baseball skin over it. I could burn the numbers into it.

Tell a story about an impractical thing you used for a game.

I was wildshaped into a Collosal+ Roc and the GM wanted to use the tactical battle map dispite the fact that i was 200 feet long and 1000 feet up in the air, I wound up using the great wyrm red dragon "mini" the DM had borrowed for the next boss fight.

A friend of mine were playing the highest ranking officer in a military-themed game I ran. He didn't quite know what to do with all that power and he didn't want all the blame if things went south, so he picked up a magic 8-ball and asked it for advice. On every decision.

Fun fact, within each magic 8-ball is a D20.

How many times did he get a "maybe"?

I have plans to turn my d8s into earrings, but when rolling for HP I'll be removing them so I can still use 2+ to speed things along. I'm considering making them unclippable from the actual ear-hook piece to reduce the impact on rolls.

In one of my previous games, one of the players had a d20 necklace. It popped in and out pretty easily for rolling. I'm pretty sure it was the d20 spiral necklace from thinkgeek. You might be able to base your earring design on that.

The castle was a series of Interlocking U-shaped sections, so we used actual Horseshoes to represent the size and scale.
along with the various blocks and legos used, we made a pretty awesome representation of the castle, and it only took 40 horseshoes (yay frat houses and random things we keep in them.)

once we used dm's baby (an actual, living, baby) to represent some very big monster

my group once had a DM declare they were attacked by a giant Kitten once after a certian fluffy fiend jumped on the table and started playing along, He apparently had an aura of "awwww"

Probably the weirdest thing i ever did in a campaign...
We used a dog once. and actually had the animal roll for the giant hellish dog it was suposed to represent.
The GM ordered the dog to sat, then put the dice on his head, the dog reacted by shaking it's head, which made the dice fall.

used my snow camo jacket to represent a snowy field during a campaign once... I did not appreciate the dm drawing grids on the back of it, even if it was in pencil and washed out.

Not exactly "impractical" but I happened to pick up a playset of tiny dice at a convention. Cut forward a few months, and I find myself in an ironclaw campaign a friend of mine was running. Our group consisted of a badger thief/diplomat thing, a jackal assassin, a monkey sailor, I think there was a dog bounty hunter in there too, and my character: A Bear Prison Warden who towered above everyone else in the group.

Now, for those unfamiliar with ironclaw, the biggest dice you will use in the game are d12's, but we all still had d20's with us, so that's what we used to mark where our characters were on the map during combat. Guess who just so happened to have the tiniest d20?

This annoyed the DM so much he eventually forced me to use one of his dice as a marker.

@Malroth
Awwww... so cute!
My home-made Christmas-cards also know the feeling of being attacked by a giant cat...
But she wasn't cute enough to get away it XD

baseball sized CAST IRON d20?

that would weigh a good 10 pounds or more.
how would you even roll that sort of thing