I try to use all of my pens equally, but the most conveniently located is a Hongdian 1851 Forest Purple EF that my wife gave me. I keep it inked up with iroshizuku murasaki-shikibu.

I have a Lamy Safari, daily driver for about 4 years now. I run a chemistry lab, so I still do a lot of writing.

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.

I use my FPR Indus with FPR ultra flex nib every day. Mainly because my only other fountain pen in working order has a fude nib lol. The flex nib makes it versatile for both writing and drawing.

Platinum Preppy lol. Just a good knock about pen. Currently I use my other pens pretty interchangeably for letter writing and journalling. But the Preppy takes the cake for the most general use. Second to that would be my Pelikan Twist since it's also a nice knockabout pen and with a medium nib (Preppy is F), I use it when I want to jot something down that really stands out with thicker lines.

It varies over time, but right now a Safari with a Chinese stub nib, and a "special alloy" Pilot Capless. For intermittent notetaking, the Capless is a particularly useful pen.

My EDC is made of three fountain pens:

• Lamy Safari (ef nib, De Atramentis Document Brown ink). I use this one for sketching (waterproof ink works great with watercolors). But a Safari has been part of my EDC since the very early 00s I like them a lot.
• Around 2010/2015, I started using Twsbi, another great fp. Nowadays I carry one for their Twsbi Eco (ef, Pilot Kon-Peki blue ink) for its ginormous ink capacity. I also like its look.
• Very recently, like half a year at most, I started using a Platinum Preppy (ef, Platinum Carbon Black ink) and I must say I'm really impressed by it. Very cheap, nice (steel) nib and sturdy. Its look is the most... forgettable of the three fountain pens, but I'm fine with that, even more that, being Japanese made, they sport a finer nib than Lamy and even Twsbi who both use German/larger nibs ;)

They're all good writers and they're not expensive (Preppy being the cheapest, by far). So, I can enjoy a fine writing experience without worrying about damaging my more expensive fountain pens.

Either a Lamy Safari/safari derivative (vista or al-star) with M nib

Or my Nahvalur original plus with M nib

I've been using my Lamy 2000 the most since it's my newest pen and first "nice" pen

I have a bottle of writers blood too. It's a great colour!

Where are you from? Is diamine expensive ink where you are? I'm in the UK and I'm always surprised how cheap it is to buy.

Pelikan 140 because it's my nicest pen with a beautiful gold nib

At the moment my hocoro dip pen so I can change inks every time :)