Kill Two Monsters in One Hit Glitch
Very easy to do 9Dragons glitch that kills two monsters in one hit.
If you have more than one monster attacking you, then you can kill two in one blow by quickly switching target to the second monster for the final blow.
This will kill both, however, the second target with health will respawn when the server realises it has not really died.
I guess this could be used to your advantage if you have low HP as it gives you some time after it dies.