Which pen do you use the most and why?

I mostly use my Traveler's Company brass fountain pen fitted with a Schmidt EF nib because It's always with me attached to my Traveler's Notebook. My backup 2nd most used was YStudio's Brassing Portable which I ended up losing while traveling in Italy's Adriatic coast. I typically cary 2 pens with different colours. In the Traveler's Company pen I use Diamine's Writer's blood and in the YStudio, I was using Diamine's Hell's Bells. Having 2 pens with two inks enables me to have more flexibility in contextual jotting.