I have a combo rapidly approaching 400k with no signs of stopping. I have a few shells (no clue how many) stuck in a loop between a few turrets and two buzz saws. Every now and then two sentries shoot them too. They can't fall and they can't stop. It's pretty funny, haha. And in the time it took me to type this, the combo went up more than 100k.
 "Alice is Dead Episode 3"){kind=icon}
 "Epic Combo!"){kind=icon}