SOF is one of my favorite FPS of all time because of its replayablity factor, thanks to the infinite gibbing. You could blast parts of heads, whole heads, arms, legs, and the chars would react accordingly. You could replay a single scene 10 times and change the way you entered the room, etc, for a whole new experience. SWAT 3 had perma-decal on the bodies too, so you could see where you shot them. Awesome games.
After that, it all went to shit (can I say that here?) with the unreal ragdoll effect, followed by havok and their 'no gibbing' engine restrictions. Now it's all 'hollywood' stuff like HL2, all flash no substance.