Faber Castell Pitt Artist Pens have always had a brush tip variant. These pens come in a wide range of colors (some packaged as sets: landscape, manga). They are lightfast, waterproof, acid free and a favorite of a lot of people.
Well they are out now in a larger size: Faber Castell Pitt Artist Big Brush. All the same wonderful colors available in the original line are available in the larger size. The image at the top of this post shows the relative line quality/size of the two pens. You can see the large tip really is quite a bit larger and allows you to do some fat lines if you work on the side of the tip (as shown on the right side of the image).
Here are the tips side by side for comparison. Same great ink and pen, just larger. I got mine locally at Wet Paint. I can't find the receipt, but I think they were under $4 which seems like a good deal since the small ones are about $2.79, or so I seem to recall.
I find the large brush pen is a bit unwieldy in my hand, and not comfortable to draw with for long periods, but if you are doing large drawings, perhaps at an easel, or in a large book, they might be just the thing to really let your whole arm move and create a flowing line. I also think that at life drawing I would like them as I tend to work larger there, but I haven't tested them in that situation yet.
So if you're a fan of the original brush pen from this company you might want to check out the new larger size! It gives us more options for our visual journaling.