Well, it's called a sawfish for a reason: Marine biologist Barbara Wueringer of University of Western Australia filmed a sawfish in action and saw (heh) that the fish wielded its saw like an expert swashbuckler!
Link | YouTube Clip
Once the sawfish has found its target, it uses the ‘saw’ like a swordsman. It slashes at its victim with fast sideways swipes, either stunning it or impaling it upon the teeth. Sometimes, the slashes are powerful enough to cut a fish in half. Even less dramatic blows can knock a fish to the sea floor, and the sawfish pins it in place with its saw.