CreditsThe final credits scroll of the first release contained anti-credits that made fun of people the Monolith staff didn't like. GT Interactive made them remove this in later releases and they are were also cut out by the first patch (which is pretty much required to get the game to run correctly).
German indexOn November 30, 1999, Blood II: The Chosen was put on the infamous German index by the BPjS. More information about what this means can be found in the description.
HumourBlood II: The Chosen contains a lot of generic and cliche'd FPS elements, and the designers are self-consciously aware of this, including jokes such as a mission briefing that tells you to "push some buttons and kill some things" (that's really what it says, word for word), and a huge glowing sign advertising "Silver Key Industries."
Open Source releaseAs of 2005, Blood II: The Chosen is open source and its full code can be downloaded from the Blood 2 homepage.
ReferencesThere is a secret room in one of the levels parodying Unreal. It has a picture of a leaping Skaarj Warrior on the wall and the inscription: "I [heart] Skaarj".
Information also contributed by Maw Mickey Gabel and Xoleras