Well, there are two things: the 1959 Martin 015 my Dad left me and the 1980 Takamine I used to gig with. But if I had to choose, the Martin would win hands down. It's the guitar I learned on back in the 60s and 70s. It's also the guitar I played my first high school concert on when I was fifteen.
My Dad found it on a mothballed ship in 1962. He was part of the crew going through looking for last minute details that needed attending before the ship was towed off to the scrapyard and he found it lying on a bunk. Someone had stove in the side and left it for dead. My Dad, always on the lookout for a bargain and knowing what a prize he'd found, asked if he could have it and his crew chief said he could.
So he took it home, slathered glue on the stove in side and wrenched the broken bit back into place. He played it like that for over 30 years before he finally took it to a luthier and got it fixed properly. In the meantime, it's picked up scratches, scrapes and dents from thousands of campfires, sing-alongs, etc. I even put a few in it myself when I was too young to know any better.