I'm sure this has already been analyzed and commented on at length by half the comic book reading internet, but there was a blink-and-you'll-miss-it moment in Deathstroke #6 that suggests Midnighter might have been responsible for the "death" of Slade's son Grant (the first Ravager, pre-Flashpoint). This could be way off the mark, of course, but if it's true it sets the stage for an enmity between two of the biggest badasses in comic books.
How many other characters do you know with a chin-spike? There have been a lot of new ideas coming from the new 52. Some were good and some were terrible. But if this is true and there are plans for a Deathstroke/Midnighter rivalry, I'll read the sh!t out of that.