I can't pick just one favorite BIB. I have a few.
As far as current offerings go, I'd pick EW BIB and HH White Label 6yr BIB. Both really good, and both reasonably priced too. With both, you get more than what you paid for, for a change. Great value pours IMHO.
For dusty BIB's, I like Old Fitz BIB and Old Forester BIB. Doesn't get much better than these two. Personally, I think I'd give the edge to the Old Forester BIB. I know a lot of folks here would disagree because of the SW connection with the Old Fitz. Just my personal preference.