Things that haven't been inventory items... yet

[Oddysseus]

Glad to be of service.  Here's another idea:

magic spell that can bring inanimate objects to life

This could create some very interesting puzzles:
Table too heavy to move? Use the spell, and it gallops away!
Can't figure out where to go? Use the spell on a map, and it will give you directions
(with a snooty accent and general attitude of disdain, of course)
Locked door? Use the spell on it and then convince it to unlock itself.

Damn, I'm not usually into fantasy games, but this is starting to sound pretty good.
I might have to make this game myself one day.

Until that day, feel free to use this idea in your own game.  See how many puzzles you can come up with that stem from this one item.

[TerranRich]

This could be a way for the player to use ordinary items (or unrelated items) in a totally new and different way.

Something like using the "detangling cream" with the "T-remover" in Leather Goddesses of Phobos and getting "de-angling cream" for the king.

But I digress. Here's some I could think of:

a mouse cursor (just the cursor itself - maybe for a game where you are "inside" a computer)
silly putty that can talk to you - and be quite silly while doing so
a cup holder, ripped out of a car
a drink coaster
a key ring
a pair of cosmic-ray glasses (x-ray glasses that were made incorrectly)
a Styrofoam particle (those little white dots that come off when you break a piece of Styrofoam)
a used toothpick
the foam that covers one ear piece on headphones
air (it's air in your lungs, and you're holding your breath until you use the item on something - i.e. blow on it)
a "Draw Two" Uno card
a graphic tablet pen
a bottle cap

Correct me if any of those have already been inventory items.

[Oddysseus]

I can't think of a specific example, but a bottlecap has to have been used before.  It just has to have been.

I think the "air in your lungs" item is especially clever, but it would probably make more sense as a gui option: "blow on."
I also like your idea of "silly" putty, because if there's one thing adventure games need more of, it's bad puns

For my next contribution, I'm just going to steal from Legacy of Kain: Soulreaver.
-What if you could carry, say, a portal to another realm around with you?
The other realm is like the current room, but objects are moved around, certain doors are unlocked/locked, and of course, everything just looks really warped and creepy.

This idea could also work for "vision" items, like:
Nightvision goggles
X-ray specs
Your cosmic-ray glasses.

You could also have "spiritual vision" items, i.e. you could see whether people were good or bad.  Good people look like angels, bad people look like demons.  It would be especially cool if you got this item late in the game, and you suddenly realized that a character that has been helping you for no apparent reason is actually an evil guy leading you into a trap (It's a trap! It's a trap!... sorry, my inner Admiral Ackbar took control there for a second).

[TerranRich]

What about an inventory item that makes the entire room reversed left-to-right (like a mirror)? The possibilities would be endless.

More I thought of:

one of those arrow-through-the-head hats
a single green pea
an unfolded bed sheet
a re-writable HD-DVD
an iPhone
a used cup (empty, but has dried-up soda or juice at the bottom)
an umbrella pole (missing the canopy part)
a "six-shooter" alcohol dispenser
a wet paper bag
a can koozie (never saw one of those as an inv. item before)

Some of those might be unknown to certain people, so let me know and I'll clarify

[Oddysseus]

A can koozie could be used to... fix a leaky pipe?
Also, the wet paper bag intrigues me... not sure why.

Anyway, I had a bunch of ideas all at once, so I'll just dump them in this post.

You mentioned an antigravity generator in your game (very cool idea, by the way), and someone way back in this thread mentioned suction boots.  The logical thing would be to combine the two: antigrav boots.
My original idea for using them was to get an unreachable item on the ceiling.  Then I realized that you could use them to make some really unique spatial puzzles.  Imagine an M.C. Escher drawing turned into a playable maze: walk up the wall, then jump to a platform, walk around the other side of the platform (going from upside-down to right-side up in the process) jump to another platform, etc.  You wouldn't have to script it like a platformer- the jumping would just be a canned animation triggered when you click on the right hotspot.  The tricky part would be drawing it so that the player could easily judge the distance between platforms, what was higher/lower, etc.

My next idea would be an inventory item that actually inconvenienced the player, rather than helping him.  I'm thinking specifically about a parasitic creature that latches onto the player.  He would appear stuck to the border of the inventory box, rather than in an item slot, and when the mouse cursor hovered over him, he would grab it, and not let go until you shook the mouse back and forth a bit.  Preferably, you would change the default pointer cursor to, say, a hand pointing.  That way, it would be immersive "It's got my arm!" rather than breaking the forth wall "I can't click on shit!"  I have no idea how you would script something like this, but I believe it's possible and I KNOW it's kickass

And lastly, just a throwaway idea that came to me out of the blue:
The game developer's mind could be an inventory item.  That way, you'd always be able to solve those nonsensical, "what was the designer thinking?" puzzles.
Alright, basically it's a cutesy version of a hint system, but I still think it would be funny if using it would get responses like "Duh, obviously all you have to do is use the jellyfish on the horse testical and the magnetron.  This is just common sense, people.  It's simple!"

[TerranRich]

I've always loved the idea of a "thought" inventory: i.e. items would be thoughts, ideas, or desires.

Also, Oddy, a lot of your ideas are awesome. Antigrav generator used on boots to make antigrav boots...so simple I woudl've never thought of it. It gives me an idea for my game actually.

More items:

the LCD screen from a calculator
the cap to a pen
a digital camera memory card
a silicone implant

[Oddysseus]

Not sure how the thought inventory would work, but it is a cool idea.  Like, you could give Love to a princess or Loyalty to a king or Eternal Disdain to your sarcastic sidekick.

What would a pen cap actually be useful for?  Hmm... I guess you could store very small amounts of a liquid in it.  Like... a mermaid's tear as an ingredient for a potion.  Though why pens and mermaids would exist in the same world is beyond me.

The silicone implant is a great idea.  You could use the shrinkray I mentioned earlier in reverse to make it into a beanbag chair. 


As for my addition to the list, I think it's already been said, but:
-intestines.

It's actually part of this idea for a game I had: You're a zombie, and the only inventory items you use in the game are parts of your own body.  Like, your intestines would function as a rope to cross pits, or a whip to defeat enemies.  You could pull off one arm and hold it in the other to grab things that are just out of reach (and too slippery to lasso with your intestines).   You could detach your eyeball and stick it in holes to see things you couldn't otherwise see.   And you would use your teeth to bite people, obviously.  Also, eating brains would give you "super strength" that you could use to smash through locked doors, etc.

And you could talk to any object in the game, but everytime you press the talk cursor, you would just shout variations of "GRAAA!" or "Splargh!" or something totally random.

[TerranRich]

LMAO, I love that idea! You should go for it! I'd love to play that game.

Oh, and to stay on topic, more ideas...though a lot of them may have been used before:

a packet of sugar
a highlighter
the metal spiral part of a notebook
an embroidered patch, ripped from a hat/shirt/etc.

And remember: all inventory items have a use, no matter how weird, out of place, or unusual.

[Krysis]

An alien?

[Oddysseus]

The metal spiral part of a notebook?  Brilliant.

Here's a few more:
Darkness
Fog
Earthquake in a can (I think this was in a Road Runner cartoon once)

[FSi++]

Sorry to interrupt, but mouse cursor was used in Richard Longhurst and the Box that Ate Time.

[G]

At Space Quest 5 you carry an alien in your inventory

[radiowaves]

Hmm, now this led me to thinking that I haven't seen any liquid nitrogen tanks as inventory items yet. Are there any? Or chemical waste?

[TerranRich]

Space Quest 5 I believe. Or some sort of gas.

[Saberteeth]

Hmm, now this led me to thinking that I haven't seen any liquid nitrogen tanks as inventory items yet. Are there any? Or chemical waste?

Larry Vales 2: Dead girls are easy. You get liquid nitrogen from the local mortician.

[Mats Berglinn]

You also get liquid nitrogen in Grim Fandango.

[Oddysseus]

A didgeridoo
A lightning bolt
The true name of God
A vowel (as in "I would like to buy a vowel," or maybe you meet a fantasy character with no vowels in his name, and he'd really like one to make his name easier to pronounce)
Estrogen
Automatic sex change device

That's enough for now.
(Your turn, internet!)

[radiowaves]

Holy macarony.

[TerranRich]

...or maybe you meet a fantasy character with no vowels in his name, and he'd really like one to make his name easier to pronounce

Heh, you mean like a Welsh name?

[MoodyBlues]

* The color red
* A fairy
* The Eucharist
* A handful of dirt (?)
* Uncontained water
* Your soul
* A harmonica
* An NES cartridge