You could concentrate the iron in a victim's blood and then rip it from their chest (or head... or stomach... or whatever suits you). However I don't think a Toa would do that since they can't kill their enemies. Maybe they could do that on their arm or hand or something to disarm them, or their foot to immobilize them. This same process could be used to stop bleeding and perhaps make it clot faster.
This would take a tremendous amount of power, definitely too much for a Toa to even have in the first place, even if they have the Nui Stone, but you might be able to briefly increase or decrease the gravity around yourself by a macrocosmic amount for only a nothingth of a second and warp time, allowing you an extra couple of seconds to dodge that bullet that is about to cause you so much trouble. In the process, though, you might just turn yourself into a black hole or something.
1) You could vibrate something at such a frequency that it disintegrates Jericho style.
2) You could vibrate atoms until they catch fire, allowing even metal to go up in flames. Or you could do the opposite and freeze atoms by making them vibrate at a lower frequency, perhaps even immobilizing an enemy.
3) If you let out a frequency at a certain pitch, you could give somebody extreme headaches and nausea, even if the frequency is not within their hearing spectrum, allowing you to attack them without them knowing that they're even being attacked in the first place. In theory, prolonged exposure to this will cause your organs to hemorrhage or in extreme cases even explode.
1) You could create a fake reality within a person's brain that could either make them vulnerable and unconscious, or calm them down so as to reduce stress or shock.
2) You could numb pain.
3) It would take a lot of energy, but you could take control of the brain stem and resuscitate somebody by starting their heart. You could also revive a brain dead person if they've only been that way for a few seconds. Then again, you could do the opposite...
You know what, I'd have to look some stuff up to think of this. Maybe you could somehow use it to cause nuclear fusion which could create a miniature sun, but as great of a weapon as that would be, even a soccer ball sized one would probably wipe out... well... a large enough area that even somebody with a kakama nuva probably couldn't make it out in time.
You could skin somebody alive from a distance with a high velocity blast of this stuff. Nuff said. NEXT!
You could create miniscule jolts of electricity in peoples nerves to create muscle spasms or even control a limb, not to mention what you could do to electricity.
Fire is definitely not the most versatile element.
Other elements can probably do cool stuff too, but not much else comes to mind at the moment.