I am sure you have tried tons of coffee flavors but I do have 2 that I am very fond of. The first is the FSUSA Coffee/Espresso. That one is pretty strong and very close to black coffee. The second and my favorite is the Vapor Station Cafe Sumatra. That one is truly a coffee that is so strong it bites you back.
Vapor Station Cafe Sumatra:
Sweeper and Sypnot Johnson Creak sampler and the red oak sampler