You are getting some good advice here,
xanderzuk, both for thru-hiking and for other outdoor activities. I caution you that the requirements for these activities are not always the same.
While it's not exciting, and may seem counter-intuitive right now, a 1oz. $10 keyring-type Swiss Army knife is what's needed
for thru-hiking the A.T. I carried a promotional
Victorinox Classic with a local power company's logo the entire way from Georgia to Maine and never needed more knife. What will you use/need a knife for? Cutting 0.25" cord, your toenails, and food containers. That's about it. You'll use the scissors more than the blade. White gas or denatured alcohol is your fuel, your brain and a stout walking staff your protection. If every potential thru-hiker was out chopping down trees in that narrow corridor, that strip of North Georgia would look like
Moab, Utah.
There are a lot of folks who start out, for that amount of space. You'll also be too tired to gather firewood most days, and you should not count on building a fire as part of your routine, if only because dry wood is often scarce, especially on a pre-hypothermic, rainy, 35 degree day.
You are getting some great advice about some fantastic outdoor knives. I've found a couple new ones for my wish list reading this. Many of those knives are just not suited for
this specific, atypical, crazy(?)
, activity you'll be undertaking. While a thru-hike shares a lot of similarities with a camping trip, it also shares a lot of similarities with a marathon. Heck, you'll do marathon-mileage days while you're out. A saw, ax, entrenching tool, survival knife, and firearm are not things that fit with the marathon-like aspect of a thru-hike (carrying everything
for six months, back-to-back big (20+) mile days, stress on knees, etc.) of thru-hiking.
You'll be hard-pressed to find anything as large as a
Gerber LST on a thru-hiker, at least after the first +/-100 miles. At the first road crossing with a store, I sent home a large Gerber knife, a can of mace, and a large compass. Hiking 15-20 miles every day with a pack over many ups and downs will make you shed anything you don't use every day and doesn't perform multiple functions; the end of your toothbrush, the cardboard core of a TP roll, the too-long straps on your pack, pages of a partially-read book, etc. Not kidding. I knew
one finisher who had a cell phone - she mailed it to herself at each new town so she could call her folks then mailed it forward to the next town. Your knees will need to last 2200 miles, and pretty quickly they will feel like they are blown out after sitting still for more than a few minutes. All that to illustrate: Pack weight is very important.
As for firearms, I know the forum on which we are posting, however this is not the trip for carrying. The weight, legality, necessity, etc. are all reasons to forgo this on a thru-hike. The weight issue is addressed elsewhere in this post. As for legality; the A.T. stretches over 14 different states and passes through more than 60 federal, state, and local parks and forests. In some parts, the Trail “corridor” is only a few hundred feet wide. You will have extreme difficulty complying with all of the legal issues. Realistically, I do not think it would be possible. Check the threads here about folks just trying to comply with CCL issues, reciprocity, on a car trip. Regarding the necessity (all things considered), I believe the A.T. is one of the safest places you could be. How many acts of violence were on your evening news last night? How many can we point to on the A.T. over its more than 50-year history?
As for the Warren Doyle suggestion, I have met him on the trail. The poster above was correct about Mr. Doyle's enormous amount of miles under his belt, and about his personality. He does offer supported trips, but consider whether that is the experience you are seeking - paying someone to tell you what you will eat, where to sleep, who you'll hike with, how to hike your hike - for six months. While this is an appealing option for some, this is contrary to what I most enjoyed out there and it's not what I imagine most are seeking.
Visiting
whiteblaze.net is a great suggestion. That is a forum by/for people who have done and will do what you are attempting. That is where you'll find the most relevant information. Remember, this is something very few people even try to do. Of that group, only about 10% are successful. It is an unusual thing to attempt and not something many people have experience with. As suggested before, seek out those who have long-distance hiking experience. (Bryson's book, A Walk In The Woods, is good entertainment but is not an accurate description of an actual thru-hike. A good resource would be the
Pacific Crest Trail Hiker's Handbook by Ray Jardine.)
Congratulations on deciding to attempt a thru-hike of the A.T. It is one of the most rewarding accomplishments and learning experiences of my life. I'll be glad to chat with you if there is anything you'd like help with or have questions about. You can be one of those 10% who finish!
(All this is not to discount the other advice you are receiving here, there are a lot of smart folks on this forum, it is just an unusual subject about which I am very familiar. Wow, I came here enjoying learning from this great group of folks. Didn't expect to hit on a topic I'm familiar with. Now back to "student" mode.)