Disciples III: Renaissance has gone all demo-y. It's a deeply hexual turn based fantasy battler that deserves a bit of respect. You can read our preview here to get an better idea.
The demo lets you play as the Humans (pfft), Elves (pfffffff), or Demons (yay!) through a big tutorial and the early stages of each race's campaign mode. It's 3.7GB, though, so you might want to go for a quick cuppa as it drinks your download cap.
Download it here . Man, I wonder what the Demon's campaign mode is like? "I WAS A SIMPLE TORTURER, BEFORE THE HUMANS STOLE MY TORTURE VICTIMS. WE SHOULD REALLY KILL THOSE GUYS."