One rifle..................I have a ton of .22lr but I also have a couple pistols. Sentimental rifles would be my model 70, 30-06 I bought new 49 years ago. The 22-250's I have are tack drivers and I have plenty of supplies to load for them, but they are 1-12 twist so heavies won't shoot well. That leaves my 260 that I screwed together a few years ago, LH Savage action with a Shilen Select 1-9, 24" barrel, very accurate and I have plenty of loading supplies for it too.
The fact I could keep my pistols and muzzleloaders, I'd keep the 260. If it was only one firearm period it would probably be my Tikka T1X 22lr. Even though I have a bunch of ammo for it, not being able to reload for 22lr troubles me.