So, everyone has been helpful so far, but I now need to really tax or task the international members.

Most of my previous international travel has been at the behest of my Uncle Sam. It was most often in green aircraft, but occasionally in charter civilian jets. Knives were never an issue, because everyone always had more than one firearm (machine guns, pistols, etc.)

Now, my question is this: What knife is legal for everyday carry in your country?

I have spent 44 years staying out of jail, I spent 8 years putting folks in jail, and I don't plan on going to jail in my life. Especially, because I accidentally packed the wrong pocket knife.

Thanks in advance.

Ok, lets start with Germany.
Basically some knives are illegal, some restricted for carry and the rest is Ok.
Firstly there a outlawed knives: butterfly or bali song, gravity operated knives and knives with their blade perpendicular to the hilt (push dagger style). You are not allowed to own them. Don´t even bring them.
You can´t carry accessibly fighting knives (double edged or advertised as such), fixed blade knives with more than 12 cm blade length(that is a little less than 5" and yes in some regions that 1/4" might matter), folding knives that can be opened and locked one handed. Size does not matter here, switchblades are included. This the opinion of the federal police (BKA) some knife enthusiasts may not share this opinion. If push comes to shove, judges are going to share the opinion of the federal police. If you carry one of those knivs, you need a reasonable cause. If your German is not fluent, don´t carry. You might be in for some unpleasant experience. However you can have them in a locked container.
Fixed blades that do not fall in one of the above categories, non-locking folders and locking folders that need both hands for opening are Ok for EDC.
Now for some policy:
If you are ask by a LEO why you carry a knife never ever mention selfdefence. The term "brotzeit" would describe a reasonable and accepted cause.

In Iraq, we weren't allowed to carry firearms, but we could carry any knife we desired. I even saw some folks walking around with what I'd consider short swords. My choices were fixed blades from 6 to 14 inches blade length. I also had a couple folders. We carried these around the IZ, out in the red zone, and on various bases without any consideration.

I sure wish they hadn't taken our FALs away. I'd much rather have had one of those.

Someone asked me why I had such a big knife once. I answered matter of fact: "For lopping heads, of course." They choked on their coffee.

Not everyone had a sense of humor about it, though. Apparently a big man holding a big knife wearing a shemaugh wrapped around his head is cause for concern to some, even in Baghdad.

I undestand that Israel is similiar. It's not a knife-carrying culture, and there are so many metal detectors and security checkpoints that hanging onto your knife may prove difficult. Like Germany, knives for snacks are acceptable, but self-defense is a no-no.

Mexico - Mexico has very strict weapons laws, and even the smallest pocket knife will get you into a boatload of trouble. It's justice system is "guilty until proven otherwise" and jails are notoriously bad (you may need to buy your meals if you want to eat). I cannot speak for knives as part of legal activities (i.e. fishing, cooking, tool kit, etc.), but EDC knives are strictly forbidden.

UK Legal Carry explained.

https://www.youtube.com/watch?v=DbHMBEtFJK8

Do not ever show off your knife (even if UK legal) in Public in the UK to folks you do not trust. They may call a Policeman.
A lot depends on your demeanor, attitude, age and how well your dressed.
The Police in Scotland for example are looking for 'Bams', There is a big difference between the city and countryside cop.

https://www.youtube.com/watch?feature=player_detailpage&v=uZErqrwkbMM#t=600

i.e. Countryside Policing

https://www.youtube.com/watch?feature=player_detailpage&v=YLnv7gC3Or0#t=800

In Germany there is a variety of knife-carrying subcultures. At some events (e. g. trucker or motorcyclist festivals) most people open carry. Generally LEOs are cool with that. When they ask about the why, they usually smell a rat. Just don´t give them the impression that you are looking for trouble.

I check the laws of the area before I go there. I also see what people on the Internet are saying to get a little "street knowledge". I can get a general sense of a place if they have silly laws like, "A permit is required for possessing a steak knife outside of a restaurant." I made that up, but you get the idea. If I see a law like that, I'll carry one of my wimpiest knives if I carry at all. It has a 1.75" blade and requires two hands to open.

Outside of clear laws, I follow the general rule of being discrete and carrying a non-tactical gentleman's knife/tool.

Anyway, the original question is super broad. For anybody who answers for their country, somebody else can give 10 caveats to the answer. The USA doesn't even have consistent knife laws among the states. The states don't even have consistent knife laws among the counties. So, I travel with the notion that every country does not have consistent knife laws throughout their entire country.

Here in the UK, the carrying of ANY offensive weapon (not just a knife)is prohibited unless one has a good reason.

A good reason NEVER includes self defence. Good reasons can include being a chef or cook, or needing a knife for ones work, or moving a knife from one place to another such as taking a newly purchased knife home, or moving the contents of a home to a new address.

The police have very considerable discretion as to what is permitted.

In the past, the carrying of a small folding pocket knife with a non locking blade of less than a certain size was permitted, but this is no longer the case.
A Swiss Army knife USED to be permitted, but is now regarded as an offensive weapon unless one has a good reason to carry it.

In practice, the size of the blade and whether or not it locks can be a deciding factor.
For example a Leatherman tool with a locking blade is looked upon less favourably than a non locking Swiss army knife. But this DOES NOT MEAN that the non locking blade is automatically "legal" or "permitted"
The circumstances of carrying the knife also make a great deal of difference. A chef carrying a number of knives too and from work in a bag or box should be fine. The same chef carrying a single kitchen knife to the local bar might well be found guilty of carrying on offensive weapon.
A scout carrying a knife well packed inside a backpack or other luggage on the way to/from an outdoor activity should be fine, the same scout carrying the same knife on their belt MIGHT attract unwelcome attention.
An engineer carrying a Leatherman tool in a tool box should be fine, carrying the same Leatherman tool loose in the pocket MIGHT attract unwelcome attention.

No one under 18 may purchase a knife, a 17 year old living on their own should ask someone 18 or over to purchase them a kitchen knife or DIY tool.
Retailers are required to ask for proof of age before selling a knife, unless the purchaser is clearly over 18. IME retailers DO check before selling pocket knives, but often don't bother for kitchen cutlery or workshop tools, though they should check before selling any knife or "bladed tool".
Almost any type of knife or bladed tool may be lawfully sold to anyone 18 years or over, though a few types that are considered to be especially dangerous and/or to have no legitimate use are banned outright and may not be sold, manufactured or imported, IIRC there is an exemption that permits museums to acquire such items.

I am not going to a region that active without serious firepower.
Including the ability to choose my own exit stragety. I will not become a part of anyone's propaganda movie.

We aren't scheduled into hot zones. Just warm zones.

None of the knives will really be for self defense. If things get that bad, I lost already.

I just want a pocket knife for edc, and something in my bag for the unexpected at work.

Since I am in telecom, (even as a project manager) everyone has the ubiquitous Klein Splicer Kit.

http://www.kleintools.com/catalog/cable-splicers-knives/cable-splicers-kit-free-fall-snip

So this and a SAK farmer may have to be it. I am glad I asked. I assumed everyone was allowed a lock blade as they are safer than non-locking.

Thanks for the responses so far.

Oh, and No Mexico at all.