Most of my 40+ pens have interesting colors in them but a Parker Sonnet with a factory italic and a Hua Hong HH-8 have black in them. The Sonnet is really dark with Quink black at about double saturation (evaporated, filled again with ink without cleaning it out) and the HH-8 has a 20+ year old generic black cartridge I had to add water to. I'd kinda like to use them, but feel guilty sending a penpal a letter in boring ink. Kinda feel the same about unsaturated blues like 4001 or Waterman.
I used to have a Vac 700 smoke with 80% Noodler's Black in it. Since that's waterproof, I used it for addressing envelopes. Not sure how, but it left a film in the barrel I had trouble removing, so that pen's empty and waiting for me to figure which of 50+ (100+ ?) untried colors to put in it.