I am trying not to become an ink junkie but, as a business owner, I enjoy these three inks as I consider each one of them to be "professional" in their own unique way:
Parker Quink Permanent Black: This is an ink that will write on almost anything and not assault inexpensive paper. It even has a good track record with thermal paper. I use this in my daily knock-around/carry pen which at the present time is an upgraded (with special cap) Hero 616. I can loan the pen with abandon and know that it will perform well thanks to the Parker Quink ink. The combination is quite smooth and I have given away several of the 616's loaded with Quink Black.
Hero 232 Blue Black: Hero 232 is an iron gall ink that goes on blue and then goes to almost black or a heavy muted blue on most papers. Like Parker Quink, it is very well behaved on inexpensive papers. For me personally, it happens to dry on my company stationary to the exact color of dark, muted blue in our company logo. It is the ink I leave in my Levenger Truwiter (medium nib) and it generally is with me when wearing a coat and tie.
Levenger Cobalt Blue: This is a dark blue that pops. While it is less than kind to inexpensive papers, it is a wonderful color for personal notes either for business or whatever. This is the ink presently in my 1949 Parker 51 and is also with me for business meetings and the like.
Perhaps you noticed the order in which I placed these inks. It is the same order that I tend to consume them with the Parker Quink being my daily go-to right behind the Hero 232.