Do everything I want to do, while alive, no matter the drawbacks, like not having enough time, or money, or social status not allowing it. No matter how impossible it looks, there is always a way to achieve your dreams and not doing anything about it, is wasting a life... in my opinion :) Build or significantly kick start the creation of the first conscious AI. I see a big fat jigsaw of potential contributiory parts in the world now and am convinced it will be plausible. Though I suspect it'll be like lighting touch paper more than carefully crafting the end result :)
There is not a single big dream that I have - I have many dreams and working on realizing them one at a time (tried realizing them all at once, and it did not work out).