In the event of civil unrest, in other words if everything went to hell?

AR
Gas piston Type AR
AK or its variants
SKS
FN FAL type weapons
etc

I'm thinking probably the AR type weapons since one could get parts, mags, ammo, etc from the nearest National Guardsman in an emergency.

I would want an AR, lots of bullets and lots of magazines.

Keep it lubed with Break Free [in my area]and no problems.

If you are one man, alone in the wilderness for months on end with your rifle in harsh conditions, an AK-47. It will always go bang and it is much better for taking game than a .223.

Otherwise, an AR-15 because you can get parts for it, and every National Guardsman carries 210 rounds of .223 ammo which he may choose to share with you.

For shooting engine blocks, and FN-FAL.

If the Chinese invade, there will be plenty of SKS lying about.

You should have at least one of each.