I thought I would pass on a few tips on one of my favourite pens. The Pilot parallel pen. The nib comes in different widths and they are really cool to use with the thin edge too.
Walnut ink on cold press watercolour paper
I used my pen for the lettering and the thick and thin wavy lines on the right side of this page.
These pens have cartridges and they write really nicely. And you can travel with them easily as you don't need to dip them. One thing to note is they use water soluble ink which can be a drawback for some purposes. This is also cool thing too. One thing I do is to write with a really wide nib on some nice quality paper and then spray it with water and let the ink run and drip. You can it drip a little or a lot whatever your preference, then let it dry. Once its dry, I go over the lettering again and it really pops but has the cool drippy effect in the background.
The lettering is walnut ink and I also used one with olive green ink around the blobs.
You can use any water soluble ink in these pens. I got a little tool called a pipette which works like an eye dropper and have bought some lovely French inks to use in my Pilot pen. One great tip I heard and I do it myself now is to not even bother with the cartridge when I refill I just use the barrel of the pen which holds way more ink and I don't have any leakage problems. And my last tip is I love walnut ink and you can use it too in these pens. Just make sure you mix it really well and not to thick so it flows nicely.
And you can see the pen itself in detail here to find out the basics what comes with them in the package. I purchased mine at my local art store, Island Blue Print but you can also order them online from Dick Blick and even Amazon too.