My absolute favorite is Penhaligon's Opus 1870. From there, in no particular order, I enjoy:

Penhaligon's Blenheim Bouquet
Penhaligon's English Fern
Truefitt & Hill 1805
Truefitt & Hill Trafalgar

I still have several scents from these houses to try, as well as other makers. The list will certainly grow. But it'll take an absolute titan of a cologne to displace Opus 1870 as my favorite.