my vote goes to mac baren navy flake, it's not overly drenched In rum but you can taste it, also it is a very easy flake to work with, the moisture is just perfect to rub, cube or fold and stuff straight from the pack.
As a bit of a curve ball I would also recommend ennerdale flake as that has a decent rum flavour (although I would say in my opinion they use a spiced rum rather than say a navy rum) along with the other menagerie of flavours.
Also I haven't tried this one, but peterson Hyde park may interest you as it flavoured with rum and maple, this is actually blended for peterson by gawith hoggarth and gawith hoggarth do a tin called rum and maple which is a broken flake which I suspect is what is used for the peterson Hyde park.
My first rum tobacco was Royal Challenge, which I liked a lot at first. Then I tried Officers' Club which seemed to jack the rum up quite a bit. Liked that one too, but when I went back to Royal Challenge it seemed kind of bland.
From there I tried Barbados Plantation which, to me at least, seemed a bit over the top. Haven't smoked a rum blend since trying BP. Might be time to go back and see if my tastes have changed....or maybe I'll just start over again with Royal Challenge.
Just as a precaution, buy ONE rum/latakia blend before you try more. I recently discovered that I'm not by a long shot the only person who's good with latakia and good with rum, but not in the same bowl!
G & H Rum Flake sure is good.
And there's Mac Baren The Solent Mixture that has more rum in it than Plumcake, from the few tins I've had.
It's a very decent blend that is not well known and deserves to be as there is a bit more Latakia in it than Plumcake.
I've never gave it much thought before reading this thread, but I've liked every rum blend i have ever smoked. One of those that I haven't seen mentioned here is Haddo's Delight. It might be topped with brandy instead of rum, I'm not sure, but I am sure I enjoyed it.