Beretta 687 OU with a European oil finished stock that is steam bent and cut to fit me. I like the oil finish for grip and ease of repair of field scratches. The custom fit it was makes it my favourite, I think. It's also just pretty enough to make me happy, but not so pretty that I'm afraid to take it out in the rain.
I have two. My 1959 Sweet 16 and a 12 gauge SXS made in 1949 by Barovnik in Ferlach, Austria. I especially like the Barovnik because I found it sitting forlornly in a consignment rack in a lock shop in KS.
Boy, what a question! You sure make it hard. To be honest, what ever gun I happen to be hunting with that day. But, if I had to say just one, it would be my 12b James Purdey & Sons. She's a self-opener, SLE, 29" bbls, DT, English grip and splinter forend, choked IC/Lt Full and weighs in at 6lbs 6oz. I guess you could say she's my baby!