I am sure we all agree that the most important thing you can have with you in a survival situation is your wits and a little forehand knowledge, but what about what we have to pack with us? For most, I'd guess it's either going to be firemaking or a good knife.

I think the most important tool is a good knife. Even just a single small blade pocket knife significantly increases my odds of success when mixed with a little ingenuity. I can't think of one thing that would have as much influence on my outcome as having some sort of knife. It is the one thing I would have the hardest time getting along without.

[color:"green"] I dunno, my kit is like an organism comprised of various interdependant systems and tools. There is no one overall most important tool. Though, yes, the most overall useful is the knife. [/color]

I would say that depending on the circumstances that special tool would vary but I would guess my Leatherman Wave will always be on top of the list somewhere.

Matt

Leatherman Wave here.
Second is the 2AAA minimag (I use it more than the arc AAA bacause it has a bit more "throw" to the light.

Certainly in daily life the most used tool I have is my knife (In my case a leatherman wave and a Kershaw chive) followed closely by my light (asp saphire lite and 2AA maglite) In a survival situation I am not sure that either of these would be my most important tool.

In a short-term survival situation (less than 72 hours with dependance upon rescue with no escape / evasion characteristics) I would think that my various signalling devices might be my most important followed closely by my warmth and shelter building tools. Sooo.. How about, Cellphone, ham radio, mirror, whistle followed closely by mini-bic, match-safe with storm-proof matches, spark-lite, followed by paracord, twine, silnylon poncho, trashbag, spaceblanket.

In a short-term survival situation, I would think my first priority for day 1 would be shelter (I can go a day without water but I will be dead from hyothermia in a matter of hours) Then quickly there-after I would want water. I could probably survive a couuple of days without water in a temperate climate (not desert tho) So, in any situation that might last longer than a couple of days the need for water comes to the surface quickly. I would have my ziplock, balloon, tinfoil cup, laytex hose for seeps and Potable Aqua tablets in use quickly.

All of the above mentioned activities would be carried out prior to my needing a knife, gun, or any of the other more romantic supplies.

Sure the knife may be considered part of firemaking supplies but there has never been a time when I couuldn't find enough tinder, kindling and small fuel to get a merry blaze going without a knife in a temperate forest. If there are any ever-greens or birches around then you don't need a knife to gather plenty of kindling and fuel. (yes, even in the rain) The sparklite doesn't need a striker to work and neither does the mini-bic so no need of a knife there.

Just a non-romantic, contrarian view for your consideration.

In the real world designating one tool as our premium option just doesn't work. It is a usefull exercise for recognising this fact. I have personally concluded SHELTER is almost always my first and primary need. To that end my clothing and an accessable shelter; compressed sleeping bag and or 9'x9' pretied tarp are my #1.

The Eskimos say "With a knife you live"...I agree.

Troy

Something that contains clean Water. That's really the main thing, without that no knife, fire, gun, slingshot, tent what have you matters.

I don't think anyone motioned the best tool of all - your brain. I understand the intent of the question but thinking clearly and making the right decision during a survival situation can make all the difference. Having the right tools to help you and being proficient with them is also a big plus.

That being said my favorite tool when in the wilderness is my 8’x10’ sil-nylon tarp. It’s light enough to always be packed and can be pitched in minutes.

I think it depends on what you mean by "most important". Seems obvious, no doubt, but do you mean "the one I use most often" or "the one I would least want to be without in a survival situation"?

The tool I use most often is my SAK Classic, mainly because it's (almost) always on my key chain. However, if I were actually in a survival chain, I would probably trade every knife I have ever owned for a way to start a fire.

As Chris Kavanaugh says, there is no "wonder tool" that will be the ideal survival tool in all situations. Lost in the desert in summer, you could probably survive without fire but not without water. In a Canadian forest in winter, you could survive longer without water than without fire. given a cup, you could melt snow for water. On a mountain in the Andes, a spark-lite or Blastmatch would be just so much extra weight without fuel for your stove, etc.

There really is no definitive answer, IMO, because the "most important" tool depends so heavily on the situation.