here's my list.i often head out for 2 days with just this in a small sling bag
1.first aid kit(small tupperware with gauze roll and pads,neosporin,several travel packs of asprin/tylenol,match safe packed with alcohol gel soaked cotton balls and tweezers from swiss army knife,tube of crazy glue,lip balm w/ sunscreen,20' duct tape rerolled on 2 tongue depressor sticks,suture kit with added sewing needle and heavy thread or dental floss.the alcohol gel soaked cotton balls also make great fire starters.in the summer i throw in mosquito repellant wipes with sunscreen.make sure your sunscreen is good for UVA and UVB.also on the outside bottom of the tupperware is a glued strip of flat fridge magnet for holding suture/sewing needle while working,i used an advertising fridge magnet that came on the front of a phone book,about the thickness of 2-3 sheets of heavy construction paper)
2.water filter straw (seychelle is my current choice,drink right from the source if needed, 25gallon filter life,filters 99.99%)
3.stainless wide mouth bottle(cook,melt snow/boil and carry water,currently a klean kanteen)
4.blast match(easy one hand use if needed,best thing i've found for fire starting one handed that wasn't a lighter)
5.ultralight 6x10' tarp(with fabric tabs,not grommets.grommets can and will tear out,tabs can be sewn back on with your needle and thread or your suture kit if needed)
6.2 space blankets(one to lay on/string up,one to roll up in,easy to spot from ground or air if they have to send out the search party for you.also makes a great heat reflector pitched under the tarp if you make a nice bed of evergreen branches to sleep on)
7.compass with lexan 2x2 signal mirror velcro'd onto the back(also easy to separate with one hand if needed)
8.large 8" sheath knife(sheath holds smaller lightweight folding knife or multi tool,wrapped in 30+/- feet of paracord,cord secured with a few loops of duct tape)
9.3600 calorie pack of mainstay emergency rations/9 bars(I've stretched a pack of these and a 1/2 lb of jerky for four days,not easy but doable)
if i had to drop one item it would be the the compass,if the point is survival there are other ways of telling basic direction,plus i have a needle and a magnet.you can make a simple water compass from those.
if i'm feeling the need for a little more comfort or heading into really unfamiliar territory i sometimes throw in(not necessarily in any order):
9.led shake light(shake for 30 seconds = 10 minutes of light)
10.thumb fire pen flare gun with 3 red flares(easy to load fire with one hand)
11.small axe/hawk(razor sharp,haft wrapped in more paracord,cord secured with duct tape)
12.more food(jerky,ramen noodles,chocolate,drink mix)
13.wire finger saw with added 8" nylon hand loops for easier sawing(mostly in winter when fire wood will be frozen)
14.gun(glock 36,one extra mag. a nine or a 357,even a 40 with hollow points MIGHT expand but a 45 won't get any smaller,flat and light,tritium sights,hottest ammo i have on hand)
15.small fishing kit(half a dozen small/medium hooks,a few lead bb sinkers and 50-100' of line 8-12lb depending on what i have available)
finally i wear a good belt that will make a good tourniquet(heavy nylon strap type with a slip buckle that will tighten all the way down.no time to punch a new hole in your leather belt if your wounded.one that will easily carry the weight of my sheath knife and if taking it along my holstered pistol) layer your clothes and wear a good boots,and if possible,a good wide brim hat and gloves
nothing with batteries or needing anything other than me to power it.if you need your iphone,ipod,gps,headlamp,gold,silver, books,rubbers,shovels,wool blankets,bible,canoes and kayaks, etc etc etc you should probably stay home or stick to car camping.some of the stuff i have seen listed is just ridiculous.I mean really,a forklift key,a prybar?binoculars? 8 knives?
the best thing about this kit is it's light,small,cheap to assemble and really works,may not be pretty and full of the latest techno gadgets and creature comforts,but it will keep you hydrated,fed,dry and warm i.e. ALIVE for 3 days.plus you can submerge this kit and it will still do it's job.