I carry a P226 9mm with 2 reloads. I've tried carrying 2 guns at a time (p220 .45 and a Browning BDA380), but it really wasn't for me. I don't remember what article it was I read this in, but I once heard that it's not good to have too many options. When a situation arrises that requires deadly force, the article said that it was best to instantly know what to reach for, not to take an extra half a second choosing which gun would be best suited for the job. Now I don't know if I completely agree with that article, but I figure it's good food for thought.
I have, however, been considering getting a very small backup piece. I think it would be nice to have a little keltec P3AT or something like that, just in case. It makes a nice little pistol for a few things. I read a post on this forum once about how the writer had encountered a drug dealer and almost had a situation, but kept his cool, because unbeknownst to the dealer, one of his his hands in his jacket pockets was holding a beretta tomcat. It would be nice to have the comfort of knowing I had some firepower in my hand, and that isn't really possible (without it being obvious) with a P226.
Another thing that got me thinking about getting a small pistol is an article I read once in a gun magazine that pointed out the fact that a pistol worn on your hip is very hard to get to when buckled into a car. The article noted that while it is very difficult to get to a boot gun when standing, it is relatively easy to get to one when seated in a car. I was sold. So as soon as I have a few hundred laying around (can't spend that much money without explaining it to the girlfriend) I'll probably pick up a little pocket pistol.
Last thing I just thought of is this: what if the "SHTF" and you need your friend to cover you? (kind of a wild "what if" situation, but bear with me) Wouldn't it be nice to be able to hand them a weapon to do so with? Just a thought. I'm not big on other people touching my guns so this would probably not happen, but it would be really nice to have someone covering my back. Let's say for example (again, weird hypothetical, but hear me out) I'm in my room and I hear someone kicking down the front door. I can hand my backup gun to my girlfriend and tell her to protect herself if anyone but me comes through the bedroom door, and then go out to investigate. No trip to the safe, no having to leave guns laying around, it's right there, and ready to use.
Just a thought.