Does the
Zorg ZF-1 count?
Okay, okay, I admit, the ZF-1 has two relatively major drawbacks....
1: the Little Red Button...
2: it's fictional
seriously though, my "just one" would be a bolt-action .30-06, like my Savage 111, find a way to MacGuyver a 10+ round magazine for it (20 would be ideal), or just have a pile of loaded 4 rounders ready to go
as has been stated numerous times upthread, the 30-06 is a versatile cartridge, from 55 grain .223 sabots to 250 grain .30 caliber thumpers, from light varmint loads to calibers that can slay the majestic møøse, or any animal on the American continent
My one rifle would be my Savage 111, with a decent scope, and bipod, and all the rest put into ammo and training
if this was a SHTF/fend for yourself/live off the land situation, I'd basically kit myself up with three firearms, my 30-06 as my primary rifle, my Ruger Mark II bull barrel (for varminting and small-game hunting), and my Mossberg 500 for hunting birds and close range hunting with shotgun slugs
If it was a Zombie Uprising and I was sheltering in place, I'd switch over to a Ruger 10/22 (assuming the .22 is capable of zombie-brain-scrambling headshots) for the combination of vast quantities of portable ammo, quiet report, and long times between reloading (stock up on 25 round mags pre Zompocalypse), and my Kimber Custom II .45 for close-in protection