In my opinion, optics make a good compliment for emergency rifles, especially for those of us with poor eyesight, myself included. Recent US military experience in the WOT has shown that with the use of good red dots and scopes, hit ratios go way up.
Last year I got a Hakko 4x21mm scope for my Colt AR-15. This is a pretty good scope for the money; Hakko was the OEM for the Colt carry handle mount scopes. They have good optics but after I got a flat top adapter for it I never got around to rezeroing.
Recently, CDNN has started selling the Hakkos, including the versions with the illuminated reticles. This makes them a lot more useful for survival/SHTF rifles, because much of the time you'll need a rifle is when it's dark or nearly so, and black crosshairs don't exactly stand out. CDNN's prices are excellent -- last year I paid about $150 for the non-illuminated from the sole vendor I could find selling them, while CDNN has the illuminated ones for $149.99 and the non-illuminated models for $79.99. Today, I ordered one of the illuminated scopes. Based on my prior orders with CDNN I expect it'll take about a week.
I plan to mount the new Hakko on my Colt using the Leaper's adapter mount, which will allow me to put it right on the upper receiver rail. The Hakko's seem sufficiently rugged that I feel OK without an immediately available BUIS. (If I was tromping around Iraq or Afghanistan I might feel differently.) The non-illiminated Hakko I currently have will probably get moved to my Ruger 10/22, which will allow me to move the Nikon ProStaff 4x32 to my .22 Magnum.