Rohrer & Klingner Konigsblau
Rohrer & Klingner inks are some of my favourites. They are not a very flashy ink company, although they are better known for their iron gall inks (Salix & Scabiosa) as well as their super shading Alt Goldgrun.
Konigsblau is one of my favourite blues because it's a very pleasant royal blue. With so many ultra saturated and unusual inks that pop, it's sometimes nice to have just a standard, everyday blue ink.
I use it a lot for everyday writing. It has generally very good behaviour on most papers, is easy to clean out, shades quite a bit. That's not to say a lack of strikes against it suffices to make it a wonderful ink - it's just a really great overall ink. The best part of this ink is that there is just a touch of sheen to it! It's sometimes not very noticeable with finer nibs (the writing sample above is a Lamy medium nib), although if you glance at it in the right light, you can see it. In an Ahab flex fountain pen, with much more ink on the page, the sheen is much more prominent.
Sheen is when, after the ink has dried, you can see a bit of reflection or shine that's usually in a different colour. In the photo below, you can see a hint of purplish red at the tops and edges of the lines, where the ink has pooled.
I always see wonderful pictures people take of sheen in inks, and I was having a hard time with my camera, but I hope you can see what I'm getting at. Getting some sheen out of your inks depends a great deal on your paper not being very absorbent. If the ink is absorbed into the paper too much, it will look much flatter. This writing sample was done on Life Japanese Stationery Stenographer pad, but other good papers to test for sheen on include Rhodia, Clairefontaine or other Life Japanese Stationery paper. I do get asked quite a bit which inks have sheen in them, because it's an unusual feature of fountain pen ink that you just don't get with gel pens or your average ballpoint.
Other inks with sheen include: Sailor Sky High Sailor Grenade Sailor Epinard Sailor Sei Boku Private Reserve DC Electric Blue Private Reserve Naples Blue Private Reserve Ebony Blue