I have a Procyon Platinum, but I stopped carrying it because it would run dry if not left flat. I have not yet found a fountain pen that will work for me if carried vertically in a pocket or backpack.

As far as my preferred daily users, it's the TWSBI Eco--they hold a whole lot of ink and flow very well. I have rolls full of pen after pen I have acquired over the years. It's always the Eco that I go back to. I should probably focus my collection there!