When I was in school, fountain pens seemed to be required. Everyone had them and you could always borrow a cartridge if your pen ran out. Ink came in stubby blue or black cartridges and the pens had enough space to carry a spare cartridge in the barrel. Occasionally a cartridge would leak but the ink washed off most things eventually. My handwriting isn't great, and fountain pens slow me down enough to improve the script.
These days my workhorse pen is a Lamy Al-Star with a fine nib, at the far left. It has written in my five year diary for the last two and a bit years, using Levenger ink that's a dark blue/purple colour (Regal). The Al-Star just works straight out of the box, no messing around, no adjustment, it's good to go. The window in the barrel is good for seeing how much ink you have left, the metal gives it enough weight for my hand, it's a good starter pen. Mine has a converter to use bottled ink rather than cartridges.
The Sheaffer Prelude in the middle was a gift from Hubby one year, it's a dark gunmetal colour and writes really well, heavier than the Al-Star, and looks more impressive. This doesn't bleed through on my Leuchtturm notebook with the numbered pages, so it will probably be my pen for writing ideas about stories, and NaNoWriMo prep. Both this and the Lamy bleed through on Moleskine paper. The Prelude has a finer nib than the Al-Star, and also uses a converter.
Newest in the pack is the TWSBI 540, filled with Noodler's Black Swan in Australian Roses ink. I got this from The Goulet Pen Company after a yarn destashing. The nib is a "fine" but I'd call the line it writes medium. It's a piston-fill system, which is new to me but seems to get a lot of ink in the pen. The barrel is non-cylindrical so the pen won't roll when you put it down. It's a nice thick pen that writes very well.
Once you get a nice fountain pen, you suddenly realise you've been writing on crappy paper forever. Moleskines and fountain pens are not a good mix, Moleskines and gel pens aren't great either. So now I've got a Rhodia notepad for work notes, and some Clairefontaine paper for letter writing, these don't have bleed-through. It takes a bit longer than I expect for the ink to dry on the good paper, but it's worth it for notes I can read in a week's time.