Ultimately, the reality of this hits when you run out of pellets... then what? That's why I'd grab a good slingshot and get good with it. There's rocks everywhere! lol
I like the Indy or Independence for the accuracy. If you can put your game down with one shot, then you'll save ammo, effort, and time. The possible failure of O-rings, price, and weight are the concerning factors there.
Well... I guess O-rings really apply to all of those choices.
A Benji 392 or 397 pumper would also be a great choice. Cheap and light. But, it's less accurate at longer ranges and you only get one shot per pumping session whereas the FX's get 7 (depending on caliber).
A hand pump with rebuild kit would be an absolute necessity for any PCP if we're talking grid down, lights out scenario. The great thing about the PCP's is the shot count, accuracy, and amount of choices.
A springer would seem like the best choice due to its simplicity, cost, and lack of additional gear. You just have to be able to shoot it with some level of accuracy.
Personally, I'd stay away from .177 and .25 calibers. .177 is small and light. If your shot is a little off, you might would the game instead of killing it.
.25 has great knockdown power and long range accuracy but, it's more of an air hog and not readily available in stores like Walmart. Mail order won't be possible anymore.
.22 would be my choice. Good knockdown power, good accuracy, readily available. Most Walmart shoppers that have a pellet gun for their kids will have chosen .177. So, the .22's could be a little less desired and left behind on the shelves a little longer. Like I said, when they're gone, they're gone. Then, it'll be time to break out the slingshot!
Honorable mention would be an arrow shooting PCP. The ammo is re-useable until it gets broken. It also allows for MUCH bigger game to be taken.
Tom