My players are a smart and clever bunch, but that doesn't mean they're immune to mistakes. After all, most of us are kinda new to the game, so the chances of misunderstanding or misremembering a rule is pretty high. In our most recent game, one of these little, completely understandable mistakes ballooned into something that was rather, well, epic.
So, everyone's fighting this group of orcs. But this particular section of the battle concerns six combatants: the tiefling rogue Jarmangle, the elfish bard Robyn, the human ranger Feer, two melee-heavy orcs, and one orc archer. They are arranged as follows:
Now, Jarmangle's player is always looking to score his sneak attack damage, for which he needs combat advantage. And the easiest way to get combat advantage is to flank someone. But in the heat of play, Jarmangle's player forgot that you need two people to flank someone. He moved Jarmangle to the other side of orc in question, making battle cry noises for every square:
He hits! He's about to roll sneak attack when I tell him he doesn't have combat advantage. "But I flanked him!" The game stops for a moment while we explain that, no, he didn't flank him.
The next turn goes to the orcish archer. He fires an arrow at Jarmangle, and it hits. Not only does it do damage, but it pushes Jarmangle back one square--
--so now, he's flanked by the two melee orcs. Each of which attack him on their turns, using that combat advantage to thrash him within an inch of his life.
But now Robyn and Feer are determined to come to his rescue. Robyn uses her Shout of Triumph bardic thingy, damaging enemies in a close burst-3 radius and allowing all allies in the radius to slide one square. Jarmangle slides back and to the left, and now he and Feer flank the toughest of the orcs!
Using that precious plus-2, Feer strikes a blow with her mighty two-bladed sword, the Mouth of Death! The orc dies! Unfortunately, dying orcs get to make one last attack, which targets Jarmangle. Oh, and enemies killed with the Mouth of Death explode, doing 1d6+3 damage to all creatures, save Feer, in a blast-3 radius.
Enough damage, that is, to reduce Jarmangle to zero hit points.
He, of course, "got better", but it remains I think a Great Moment in 4E Combat.