Can't say anybody really stands out - possibly Leeds and Forest, but it usually varies according to games that mean something in any particular season.
Counting out local rivalries... I cannot think of anybody. Maybe Norwich? Only for reasons that I actually don't think we have a bigger bogey team. Our last win against them was 16 years ago... And we've played them 10 times since then, drawn 1, and lost 9.
It used to be Hull City for personal reasons, but its gonna have to be Bristol City now to claim the title of best BCFC.