Yep, I'm just now noticing that people apparently didn't know this. That's pretty surprising. It was first shown at E3 when one of the devs did an extended combat demonstration.
There are many executions that are context sensitive based on where you and the enemies are positioned in the environment. People initially thought that all you could ever do was kick enemies from high up locations, but there's that and quite a bit more. You can slam your shield down on an enemy's throat causing them to drown in deep enough watere. You can force opponents into burning flames, setting them entirely on fire after running them through with your sword. You can knock enemies onto spikes, impaling them. There's over 100 possible executions according to Crytek.