2. Hunting small game.
3. Hunting large game.
3. Concealability (optional but might be a good idea).
22LR ammo is very light and small, so it satisfies all of the constraints, but it's only really good for hunting small game. Even though it could be used for self-defense in a pinch, the reliability of rimfire is so poor I'd rather not. A 22 takedown rifle would be much better for accuracy than a pistol, especially beyond 20 yards, but since the rifle is also going to be fairly inaccurate past 100 yards, and can't effectively harvest large game or be used for self-defense, is it better to go with a 22 pistol for small game and a bigger rifle for larger game and self-defense?
Or would you just stick to a semi-auto pistol in a common caliber like 9mm for self-defense?
Derf26: what do you mean by poor reliability of rimfire? Failure to go "bang" or to hit and kill a human within rimfire ranges?
For myself I don't want a gunfight and would prefer to slip by unnoticed, especially when solo.
I don't expect to be taken on by bad guys who are good shots at 600+ yards so no need for counter-sniper fire. More likely is the chance of being robbed at gunpoint so a pistol would be good.
For short forays I'd go with a 9mm pistol. Longer forays outside of cities a takedown .22 might be more practical.