What with Hurricane Katrina last year, I've been thinking more about SHTF scenarios (and slowly accumulating the sorts of things that might be useful in such a scenario). My relatives, however, are not so interested in preparing. I was discussing with my wife the possibility of giving them all (three families) one of those really heavy duty water filtering systems like you see in [Backwoods Home and the like. She suggested that I might want to consider giving them guns (two of the familes have guns, but ones not very useful in a home defense situation), and while I won't be able to afford that this year, it got me to thinking about the problem of what I would give, if and when I could afford to do so.
My answer was a .357 magnum lever action rifle/carbine like my own Rossi Model 92. My reasoning was much the same as many others here: simple, reliable, easy to use, accurate, plenty of range and power for most situations, light on recoil, light to carry, and ammunition is commonly available. Sure, it has its down sides, like being slow to reload, but I think the advantages outweigh this. I also think it is easy enough to use that people like my mother and my aunt can learn to use it and they won't be put off by its weight or recoil.
Maybe next Christmas...