I would say that the most unusual that I have had would be the chocolate infused ones. Youngs Double Chocolate Stout works pretty well, as does Sonoran White Chocolate Ale. Can't really drink more than one, but is is a nice change to have one every now and again.

I recently had a Wychwood Hobgoblin Dark English Ale...It was fantastic!!! They have a pretty neat website here too, updated for Halloween.