I won't spend the cash but this is what I think is the BEST large format lens, period. Smooth yet sharp, the Cooke PS945 229/4.5:
http://www.cookeoptics.com/cooke.nsf/products/largeformat.html
These picks are all over the place but if your criteria is sharpness, then the later-newer the better, i.e. Rodenstock Sironar-S or the Schneider APO Symmar-L. But you can save some money with the previous generation Sironar-N and APO Symmar (sans L), they are 99.99999% as sharp with a few degrees less image circle. There are some older lenses that are incredibly sharp too, like the 135 Kodak Wide-Field Ektar which has a great reputation.
For portraiture and expressiveness, I like the Schneider Xenars and Eastman Kodak Commercial Ektars, especially the 14" on 8x10. But even a sharp Symmar can look good for portraits if you simply shoot with it wide-open with a round aperture and shallow depth of field. I've had the classic Brass portrait lenses too, including an expensive Verito, but I think they are only good for making mush.
The fast lenses I've had are the Aero-Ektar and 135/3.5 Xenotar and I was ambivalent, a lot of hassle or expense for not much of a gain, as well as somewhat flat/mushy and difficult to focus with such shallow depth of field. Good way to waste film....
I also consider the shutters. While Copals are predominate on most later lenses, the last of the all black Compurs were probably the finest shutters ever made. If you shop on German eBay quite a few lenses in Compurs still show up but they are rare elsewhere.
Something to watch out for is an older lens in a newer shutter or vice-versa. While it can work just fine, unless you know the history there is a chance that the aperture scales are wrong or the lens may not have the correct spacing between the front and rear.
The American-made shutters that you will find on old Crown and Speed Graphics are all very reliable and well built, much simpler and cruder than the Compurs but almost bulletproof. Making something good that isn't expensive is harder to do than it is to make something good that's expensive....