It looks like the majority of those so inclined to respond to this thread are generally in favor of or are already carrying. Maybe it has something to do with the outdoorsman mindset, where many of us are also hunters, target shooters, etc., or maybe it's because those opposed to carrying guns feel outnumbered and choose not to respond. There are many philosophical reasons to carry weapons both in the wilderness and around town, but I'll not go into them as we all already know where we stand. I would like to continue the discussion a little bit on the effectiveness topic however.
  • Certainly for human attackers, a handgun can be very effective, provided that it is used correctly, and that it is not inadvertently surrendered to the attacker. For animals, the effectiveness is even less clear.
  • For a bear, multiple shots to the torso with a large caliber handgun may not be enough to stop one, not to mention that a bear can seemingly come out of nowhere, and the first thing you see may be a giant paw with claws swiping at your head. I've heard that bears have extremely sensitive noses (this seems obvious) and that pepper spray can incapacitate one (this is not so obvious, and I am somewhat skeptical, considering the consequences of being wrong).
  • For mountain lions, you likely will never see one until an attack is underway. I have no idea whether pepper spray would be effective for one of these or not, but if the big cats are like the household ones, I wouldn't expect anything but a very well-placed bullet to stop a cougar.
  • For wolves, coyotes, and stray dogs, I don't think you'll have a problem unless you either run into a pack, or meet one that is rabid. Fending off a pack of dogs with a handgun has its obvious limitations, though pepper spray may be effective.
  • For alligators, I don't expect pepper spray or a handgun to be very effective.
  • For snakes, a gun will kill one, but once you've identified the snake, they're easy to avoid. If you've already been bitten, killing the snake will not help you.
  • I'm sure there are other hazards in North America, and there certainly are many for those readers on the other continents.
So if it makes you feel safer or you just want an excuse to carry a firearm, and it's legal, then by all means do so. Likewise for the bear spray. Just remember that neither is a panacea, and there are dangers with venturing into the wilderness, as there are with any other activity. I tend to agree with the OP that both a handgun and pepper spray make a good combination, provided they are both quickly accessible. However, neither is as effective as being aware of your surroundings and detecting dangerous critters before they get too close. The problem is that fishing is just so distracting...