Guess I'll join in on the guessing game (now a clue's been given).

I think the 'almost' guess yesterday was a compass, meaning my guess would be a Spirit Compass. I.e. a compass that can detect spirit energy, hence the second part of the task, track your competitors whilst masking yourself to stay off their compass.

I love it how Noah can surge, commanding the very lifeforce of his being, while still looking bored.

Oh no .... I already had this theory in my head yesterday, but now I am pretty sure.
If she is indistinguishable from spirit, then Garth will be able to detect her when he does his hourly spirit detection! Or at least a spirit infused mirror will cause suspicion.
I am starting to think this was a trap set up by Veda!

A single sock/glove?

A flash light perhaps?

If Noah can hide his own spirit, Ciel can most likely hide herself or be hidden too. Considering her understanding of spirit.

@Mads
Good point. Hope you are right.

I know what is in the pocket. A loot box from EA ... Open for a chance of a rare spirit technique ... Ok, I'm leaving.

Spirit-infused object, eh?

Felix's Deck of Cards?

Felix's deck prob i agree

OH is it a dictionary considering @Probored's comment

OH is it a dictionary considering @Probored's comment

And then the guards pocket rips open as the object flies towards Noah.

A deck of playing cards then?

Other than my previous guess...
Could it be: a plant, perhaps a flower?
A particular set of ski(tt)l(l/e)s?
A glitter globe?
A regular globe?
! A ball like one of Burk's?
Hair?
A comb?
A crown?
An earring?
A gun?
Gunpowder?
Dynamite?
A handkerchief?
An umbrella?
A tobacco product: cigar, cigarette?
The letter of the day, perhaps Q?
Money?
A get out of jail free card?
A joker card?
A face card: queen, king, jack?
A number card: Ace through 10?
A Kuriboh card?
A door card?
A button (either push button or for clothes)?
A hologram projecting device?
Air?
A pendant?
Garnet's pendant from Final Fantasy IX?
The same pendant (or like it) as the one the Iron Judge had? (If no one guessed it, I think this is it!)
Tobi's Lipstick? You don't get blue lips like that naturally right? ... right..?
Blubber?
Flubber?
Rubber?
Any of those objects Weird Al mentions in Hardware Store?
...
I mean it probably is Felix's Deck...
She got the whole world in her hands?

Maybe it's a flare gun?

Pocket Lint.

@Kiithnaras & datdat: Felix's cards... a nice idea, but would they really be described as being infused with Garth's spirit? It could be that she was trying to avoid giving the game away, but wouldn't simply calling it a spirit infused object, without mentioning names, have sufficed? Could be though, could be.

Failing that, a perhaps a tarot deck? Or some other highly specific type of cards?

The protagonist of Chrono Cross?