A bunch of Microsoft's old RTS games, which have been reskinned and revamped in recent years, on for 50-85 per cent off.
Age of Empires II HD (3.29)
Age of Empires III Complete (8.79)
Age of Mythology Extended Edition (6.25)
Rise of Nations Extended Edition (4.29)
Or everything, including all add-ons and expansions, for $21.99
http://store.steampowered.com/sub/91439/