This is a great thread and everyone who's been mentioned is indeed an influence to one degree or another. They are all certainly master gun builders. I guess it comes down to personal tastes... If I HAD to pick, for me it would be Bill Shipman, Jim Kibler, and Wallace Gussler. Also, Mark Wheland inspires and influences me greatly. Again, that's not to say I'm not influenced greatly by others, it's just these guys really appeal to me.
As for the old masters, J Bonewitz and L Reedy, as well as several from the York Co. school.
Ed