A very interesting post from a very long and interesting thread on this subject

A few innocuous or dual-use items:

(I think that these would all be able to get on-board with you)

fire
book of matches,
Flint rod + keys,
lens (of glasses, on tweezers in your FAK, in bino's, etc... - not sunglasses!)
100% cotton twine
Hand sanitizer - this is simply sweet smelling sterno (gelled alcohol)
corn chips ( I just learned about their use as tinder this weekend works great!)
Ranger bands
candle (avoid the trick birthday candles as they contain gunpowder)
9 volt battery and steel wool (small transistor radio and a cleaning kit) The steel wool might be the hard part of this.

signal
mirror,
whistle,
compressed air horn,
fire - see above
CD (improvised mirror)
Cell phone,
PLB,
Ham HT (my personal favorite)
Ham Rock-Mite

water
Large - gallon stand & zip ziplock
small - unlubbed condom or balloon
iodine or halazone tablets
in-bottle water filter
1-liter water bottle

food
power bars
snickers

[b[]DISCLAIMER]
These next two categories are not sanctioned but cannot be prevented. If you wish to protect yourself from misbehaving other passengers you might consider them. I neither suggest the use of these items nor would I use them myself
[DISCLAIMER][/b]

edges
I don't know what your status as LE will get you but take that as far as you can
improvised edges
CD broken in half at the appropriate time
wine bottle shattered in use as a blunt instrument
broken signal mirror
mirror removed from inflight lavatory

weapons
bandanna with roll of quarters
wine bottle about to become an edged weapon
talent and training
in-flight blanket and pillow
serving tray
serving cart
full soda can in bandanna

lighting
a photon II minimum (small LED keychain light)
Petzel Tikka or Zipka would be a good idea

miscellaneous
small travel sewing kit - this is always a good idea. Just remove siscors.
dental floss ( dental floss and safetypin can be a fishing kit) - glide dental floss is spectra with decent tensile strength and can be used to hold a shelter together.
plastic sheeting / tarp / poncho (anything from those flimsy emerency ponchos to a trashbag to a full mil-spec poncho can be used to provide very useful shelter.
More substantial cordage - always useful and permissable from a spool of nylon twine to a hank of climbing rope is up to you.
Duct-Tape! Can never have enough of this stuff!

office
notepad - rite-in-rain preferrable
pen / pencil - space pen or pencile needs to work in rain and s/b pressurized.
Duct-Tape!
stapler
straight edge / ruler (this has a bunch of uses)
Travel clock / alarm
Weather radio / sw receiver
Compass - something clip-on / keychain zipper pull
Thermometer

First Aid Kit
bandaids
moleskin
4X4 gauze (bunches)
adhesive tape
Duct-Tape!
painkillers
anti-diarheal
anti-vomit
motion sickness
Res-Q-Me tool

Evac tools
Evac-U-8 hood or like
PFD (I'm not sure you can get a self-inflating one on-board due to the pressure cansiter required to make it work)
Cordage - this would have to be substantial to work in this capacity.
Nomex gloves - invaluable if needed hardy leather would also work.

Urban destination tools
door alarm for hotel room. Door knob hanger - door stopper - motion sensor All available, battery op'd, effective intrusion alarms and light and small can be found cheap at radio-shack or expensively at Hammacher-schlemmer.
money-belt, neck pouches / walletts for valuables and id
Small mesh bag for in-room laundry
Dr. Bronners peppermint soap for laundry
and don't forget the voltage converters or your electric razor won't work.