I'll tweak it a bit.. What would be your top 10 if:
1. The SHTF, & it is the zombie apocalypse.
2. You cannot get parts.
3. You have to carry what you have, but food & water are abundant (yeah i know, makes no sense, but this is like a movie!).
4. Ammo seems to replace itself, too.. lots of stored caches of bullets everywhere!
IOW, you are in a modern apocalypse movie, where you don't really have to eat or drink or sleep, just shoot zombies, and maybe a few targets for fun.
Here would be my list, in this case:
1. semi auto 12ga w/mags, ala saiga or vepr.
2. m1a scout 308.
3. para 14.45 45acp 1911.
4. Glock 30s.
5. AR
6. redhawk 45acp/45c
7. 454 lever carbine
Most of the time, i'd have the AR in place, as it would give me the fastest shots & recovery with the most capacity. But if i needed some longer range, the carbines would fill that niche. No need for a nice engraved O/U.. no need for 22s or 9mms.
Actually, if i had to carry these around, i'd probably go with just 2, the ar & the para 14.45 (or maybe the glock 30s since it is lighter).. but there would be times i'd miss the shotgun.. i would hate to be without its power & easy accuracy. If there was plenty of ammo stashed all around, the shotgun would be nice for close range defensive work.. as long as the zombies weren't shooting back!
I guess there are a lot of 'what if' scenarios that could come up, & the firearm choice in those situations would be different, depending on the circumstances. If it were a hitchcockesque movie of 'The Birds', but with clay pigeons attacking everyone, a longer barreled, hi cap pump or auto might be nice. I might even prefer the O/U for accuracy, but reloads would be tough. If the zombie hordes were squirrels, a 10/22 would be tough to beat. but if they were grizzlies or rhinos, i'd want something a bit bigger..