i would invent something, a machine that can demolish all the rubbish that we human has accumulated over centuries. all the rubbish including plastic or all materials that hard to dissolve/break will be demolished or vanish. that will be quite helpful to decrease all the dumps we all have. and and it helps mother nature as well. :)
the next one is, a machine. alright everything will be a machine since science n technology are so advancing and you know so so so popular/ in demand/ useful/ knowledgeable. ok. so this machine can fight with nuclear weapon. honestly, i dunno what technology that can fight back nuclear weapon. but well, if we have it, i know the world still will not in peace. but i plan to use this machine to demolish all the nuclear weapon as well as this weapon that is greater than nuclear weapon so there will be no greater weapon on this earth.
i know human are so greedy they will keep inventing weapon that will become the most powerful but still at least on the moment let the world in peace.
i guessed so far these are the two innovative and world changing invention that i would invent if i can :D
maybe to u its not ;)