both my answers unfortunately are impractical, unless you wanted to tell the time during the apocolypse, of course my first item would be my Pocketwatch. simply because it's sentimental, I got it for my 21st birthday and it's my most prized posession.
secondly however would be my backpack... full of my art supplies.
I'm not taking any chances, If a zombie or whatever rampages through my house and curshes my stuff fnie, but if my stuff happens to be my art supplies, Oh I will kill them with whatever is handy at the time, even it's just my hands...
I spent too long finding a collection of art supplies I like using as much as my current set, i'll be fucked if i have to find them all over again after the zombie horde...