Favorite Blue and/or Black Inks

I know this is less exciting for most, but I primarily use my pens for work and sign lots of things which need to be either in blue or black ink. Curious within those parameters what inks everyone likes. Thanks in advance - currently have pilot blue, noodlers dark matter and noodlers blue and iroshizuku black

Edit: did not expect so many responses. Today I ordered: Waterman Serenity Blue, Iroshizuku Shin-Kai and Platinum Carbon Black….but will definitely look back to this when I need more options!