I know location has a lot of influence on what you would select, for the lower 48, I would be perfectly comfortable with one of my light weight AR's. A diminutive .223 is an acceptable compromise to me. I have put down a large doe with one shot and I've seen the after-affects of what that little bullet will do when I was in Iraq...it has its limitations, but if you do your job, it will perform. I also have a Ciener .22 conversion kit which is a great way to maintain your drills and range time without killing the pocket book. About the only item I plan on adding is a quality sound suppressor. Keeping a low profile is good before, during and after any SHTF event. I do agree that you key to survival is constant situational awareness, keep a low profile and never present yourself as a target.
In a more rural (either open range or mountain) environment, I would most likely opt for my Springfield M1A Bush in .308...as Runs With Scissors mentioned, a Buckmark or Ruger .22LR pistol would be effective on small/medium game easily up to 50 yards without destroying meat and the larger .308 is more than effective on two legs or four legs out to 400-500 yards; my Bush would also make a top "battle rifle" if/when needed.
I know you're specifically talking about rifles, but a quality pistol (that can be concealed) will probably be more appropriate for the majority of SHTF crisis and you can carry without marking yourself as a threat or target to law enforcement/military or the ignorant punk that wants what you have...just another consideration.
There are so many choices for so many situations...you have to love that

For the majority (and what I tell my co-worker/friends) a decent 12 gauge pump (Remington, Mossberg, Winchester) and quality pistol (semi or revolver...9mm, 38/357, .40 or .45) will cover 90% of your needs whether it's self defense, home defense, hunting (big/small game and fowl), show of force, etc. and relatively (especially the shotgun) inexpensive.
ROCK6