Dunhill MM965. It is a good hearty, smokey latakia blend. It always makes me smile and I'm rarely more than several days without a bowlful, if not every day. It is priced reasonably, burns easy and doesn't require a lot of relights. The new blend is helped by a little age, I try to keep at least a year ahead of my use in my cellar and that blend is by far the majority of the cellar.
Tough for me. Nightcap is my favorite blend, but it's not really an all-day for me. 965 really fills that role. I guess my choice would have to be Westminster, since I could smoke it any time of day or all day but it's still very rich and has blenty of latakia. Plus it's a very, very close second to Nightcap.