Dementia, be it from alzheimier's or something else - because I seem to have all the early symptoms, brain won't move at times, handwriting deteriorating, can't seem to get motivated to to anything, everything seems so overwhelming
Cancer - comes and grabs you and holds you fast, what it does is out of our control, it might be good to you (easily treatable), it might not (you're gone in a couple months).
Heart - while I do get chest pains, they don't worry me too much. I guess I see this as being one of the more treatable age related diseases.
Right now dementia tops the list.