Killzone should be moved to the "Doesn't work with Dualshock 1 controllers" list, or perhaps you should make a list of games that only partially work with a DS1 (like SOCOM,) and put Killzone on that list.
Killzone makes use of the DS2's pressure-sensitive D-pad. When sniping, you use "up" and "down" to zoom in and out. The harder you push either button, the faster the scope zooms. In the controller configuration screen, you use sliders to adjust the sensitivity for looking on the x and y axes. These sliders function in a manner similar to the sniping controls. If you play with a DS1 controller, the sliders move really fast, and it's hard to adjust the sensitivity to a good level.