I have two signature guitars (which is a sizable % of what I own).
1. Mike Campbell Duesenberg. I kind of wish it didn't have such a flashy paint job, because my technical prowess doesn't live up to the racing stripe. But it's just sooooo fucking gloriously well engineered. Easily the most well-intonated, stays-in-tune, plays-like-butter guitar that I've ever owned, gets a pretty wide range of sounds (bridge humbucker + neck P90), and it sounds fantastic through almost any amplifier. It turned me into an evangelist for Duesenbergs. I'll never sell it.
2. Malcolm Young Gretsch - I bought it used, after the original owner had it custom painted candy tangerine, swapped out the pickups, put a Bigsby on it, and then put it right back in its case forever. I know, I know... why would you buy a signature model and then heavily modify it? I don't know. After I bought it, I took the Bigsby off and made it back into a hardtail. It's probably the guitar I play the least, but it's just super appealing to me. I think it's cool as shit. I'll try to put a photo up this week.
(edit) Used to have a George Harrison signature Gretsch that I impulsively bought during a trip to New York, but just never bonded with it and sold it.