I don't consider any of the stuff available in tins to be bulk, regardless of how it's sold, but if I did my answer would be an emphatic Ennerdale Flake. Pretty much anything by G&H, honestly, but yeah, definitely Ennerdale.

As to what I do consider bulk, tobaccos not available in tins: any of the Stokkebye Flakes and/or their Aromatic Dutch Slices and/or Lancer's Slices and/or PL Bengal. Really it just depends on my mood. Though, I did get my first whiff of Newminster 403 yesterday and if it burns half as well as it smells when unlit it may be a contender.