I don't know if you've seen the demo of Arkham City that's floating around, but in it is our first real look at the Riddler.
To put it plainly. GIANT SPINNING BLADES OF DEATH. And if you fail to make it through the room a hostage dies. (I'm not sure if you die, but I have a feeling I'm gonna find out)
On another note I can't wait to glide over Arkham city. The new gameplay looks amazing.