Age of Empires 2.
One of my favourite games of all time. I recently found out there is HD remade version. Exact same game as the original, but it just supports the new resolutions of today. Very awesome game to play on those $200 11.6" laptops that pop up all the time. Basically you can run this game on a potato!
I bought it a while ago for $20.00 and it has been one of my favourite games to play on my microsoft surface. Very excited to see it for $3.00, because it means the wife's steam account is now going to get it as well!!