Using stairs as a sole lethal weapon. (eg: Man running after main, main uses ability, creating stairs, man falls on face and dies. XD)
I also came up with idea where you guide the hero on his adventure (like Navi from Zelda), by making controlling the elements to force him to do something, and henceforth leveling up with the player via battles. (eg. Hero running from bad guys instead of fighting, you have a choice of what to do, drop a rock forcing him (also you) to battle, or let him run, and block off the path from the baddies)
Another idea of mine I'm implementing: Think one of those games like Slender where you wander around with a dying candle/light/flashlight, etc, except with fireflies in a jar. And then you use bugs to do other things too...Bug-using strategy game. You can also get items from the ground using an "Ant Farm". Get it? lol