Reference to Ion Storm: In Hell's Kitchen, there's a basketball court (the one in which two NSF thugs are mugging a man after exitting Smuggler's). Pick up the basketball and throw it towards the hoop, and you get the message: "Basketball?! You should be playing football! Go Cowboys!" In addition, making a shot (or, apparently, getting the ball stuck between basket and backboard) results in the message "Sign him guy up for the Knicks!"

And another, a references to Roger Zelazny's books: In "building 14" in Paris, a datacube locked up on the second floor mentions a computer login as "rzelazny/shadowjack", or, Roger Zelazny, and the book Jack of Shadows.