I knew gentleman that was 100 (he literally turned 100 the year I met him). He was one of the most sharp people at the retirement home; I think a lot of it was the fact he loved the internet and gaming.
Edit: If any of you are history nerds with a good concept of time, you may have thought of something:
HE SAW CIVIL WAR VETERANS; HE WAS THAT OLD. I say "saw" because he only ever saw them in parades, never spoke to them. I asked him if they let the confederates on the floats and he just laughed and said "no" (I wish people had that common sense nowadays) . He also thought I was asking if he FOUGHT in the civil war, so that got a good laugh out of him aswell. Cool dude all around. He used to give me a lot of shit, but now he's just another grandpa to me.
It makes you wonder how much things have actually really changed under the surface when you realize that it's only their great grandkids that are still in charge of things today.