On Age of Empires II you can have certain buildings attack adjacent enemy buildings. First you build either a Barracks, Stable or Archery Range next to an enemy building (as in touching), then you select that building you made and right-click the enemy building you're next to. You'll notice the enemy's building slowly losing life and it will continue until it's destroyed. You can't stop attacking it and can be re-produced in the Conquerors expansion pack.
And while I'm on the Conquerors there's a bug where "Hoardings" doesn't give you +1000 to your castle. Instead it gives you ~120% more hit points to your castle. How cool is that?
Hope this has been interesting!