Best fight as a DM: I'd have to say my favorite was the battle with the orc warchief, Mogor the Invincible. Mogor was a custom solo monster, an orc who fought with a sword in one hand and a warhammer in the other. The sword dealt nasty damage, while the warhammer had various knockback effects.
Mogor had a special shtick: He was called "the Invincible" for a reason. His sword was the stolen family heirloom of the eladrin warlord PC, and while he held it he could not be slain - he regenerated 50 hp per round, and if he went down, he popped back up again with 150 hp. To add insult to injury, he'd had iron bands welded into place around his sword hand, so that he physically could not be made to let go of the sword.
The only way to take him down was to target the sword hand (a very difficult target, AC 28 for a 6th-level party), and do enough damage to break the iron bands and sever the hand. After that, he lost his invincible-ness and his sword attacks, but he was still a bad-ass solo.
The background of the encounter: Mogor was leading an orc army against a goblin stronghold. The PCs were not friendly with either side and wanted them both to take heavy losses. They had infiltrated the goblin stronghold through the ruins underneath it, and made a deal with the leader of a band of human mercenaries who had been dragooned into service by the goblins.
The PCs debated strategy for a while and finally decided to draw Mogor down into the ruins below the castle proper, into a big room with pillars holding up the ceiling, formerly the lair of a dragon (the PCs had already slain the dragon on their way in). The pillars were badly corroded by the dragon's acid and could be knocked down with enough damage. Some Dungeoneering checks revealed that four pillars would be enough to bring down the roof. The PCs figured this would be their failsafe; if they couldn't take Mogor, they'd collapse the roof on him and hope some of them made it out. They weakened several pillars before the fight, then went upstairs to find Mogor.
Mogor and his soldiers had just broken through the castle's defenses. The PCs got his attention and led him down through the dungeons and into the dragon's lair, where the mercenaries were waiting. Mogor burst in at the head of a horde of orcs, and the mercenaries engaged the orcs (NPC fight, handled by DM fiat) while Mogor himself went for the PCs.
The PCs encircled Mogor and hit him with several well-aimed daily powers, giving themselves major boosts to their attack rolls. This was vitally important, since it let them target his sword hand effectively. Then they set to work beating him down while the orcs pushed the mercenaries back. It took a while and he did a lot of damage, but finally they cut off his sword hand.
By this point, most of the mercenaries had fallen, and orcs continued to flood into the lair. The eladrin warlord scooped up his family sword, and the party knocked out the pillars while Mogor, undaunted, smashed at them with his warhammer. Then, as the roof started to crack and crumble, the PCs fought their way through the orcs to escape.
At the last moment, Mogor threw his warhammer aside and grabbed hold of the eladrin warlord (who had already used his fey step), trying to drag him back into the room so they would both be crushed. The eladrin made an excellent Athletics check and broke free, and one of the other PCs - the human fighter, I think - hauled him out of the lair just as the ceiling came down, burying Mogor under tons of rock. It was a hell of a conclusion.
Worst fight as a DM: I'd have to say the third fight in the very first session of my campaign, where I put a 1st-level party without a wizard up against two dire rats and three rat swarms. It was very cramped quarters - I hadn't yet learned the importance of maneuvering room in 4E - and the party lacked any effective way to fight swarms. The fighter got overwhelmed and eaten, straight from positive hit points to negative bloodied in a single round of swarm attacks. That fight was a mess.
Of course, there was also the preview session I ran with the Raiders of Oakhurst dungeon. The fight with the black dragon was godawful, just endless grinding and grinding with the players unable to make much of a dent in its hit points while it wore them down one by one. Bah.
Best fight as a player: The bridge fight Vayden described above (I was the pyromancer).
Worst fight as a player: There isn't any one fight that stands out as worst to me from the player perspective, because in 4E, the worst fights are the boring ones that slip into "grindspace," which means they're not very memorable. Some of the Keep on the Shadowfell fights were like that, as were most of the fights in our abortive "orc warriors" campaign.
Mogor had a special shtick: He was called "the Invincible" for a reason. His sword was the stolen family heirloom of the eladrin warlord PC, and while he held it he could not be slain - he regenerated 50 hp per round, and if he went down, he popped back up again with 150 hp. To add insult to injury, he'd had iron bands welded into place around his sword hand, so that he physically could not be made to let go of the sword.
The only way to take him down was to target the sword hand (a very difficult target, AC 28 for a 6th-level party), and do enough damage to break the iron bands and sever the hand. After that, he lost his invincible-ness and his sword attacks, but he was still a bad-ass solo.
The background of the encounter: Mogor was leading an orc army against a goblin stronghold. The PCs were not friendly with either side and wanted them both to take heavy losses. They had infiltrated the goblin stronghold through the ruins underneath it, and made a deal with the leader of a band of human mercenaries who had been dragooned into service by the goblins.
The PCs debated strategy for a while and finally decided to draw Mogor down into the ruins below the castle proper, into a big room with pillars holding up the ceiling, formerly the lair of a dragon (the PCs had already slain the dragon on their way in). The pillars were badly corroded by the dragon's acid and could be knocked down with enough damage. Some Dungeoneering checks revealed that four pillars would be enough to bring down the roof. The PCs figured this would be their failsafe; if they couldn't take Mogor, they'd collapse the roof on him and hope some of them made it out. They weakened several pillars before the fight, then went upstairs to find Mogor.
Mogor and his soldiers had just broken through the castle's defenses. The PCs got his attention and led him down through the dungeons and into the dragon's lair, where the mercenaries were waiting. Mogor burst in at the head of a horde of orcs, and the mercenaries engaged the orcs (NPC fight, handled by DM fiat) while Mogor himself went for the PCs.
The PCs encircled Mogor and hit him with several well-aimed daily powers, giving themselves major boosts to their attack rolls. This was vitally important, since it let them target his sword hand effectively. Then they set to work beating him down while the orcs pushed the mercenaries back. It took a while and he did a lot of damage, but finally they cut off his sword hand.
By this point, most of the mercenaries had fallen, and orcs continued to flood into the lair. The eladrin warlord scooped up his family sword, and the party knocked out the pillars while Mogor, undaunted, smashed at them with his warhammer. Then, as the roof started to crack and crumble, the PCs fought their way through the orcs to escape.
At the last moment, Mogor threw his warhammer aside and grabbed hold of the eladrin warlord (who had already used his fey step), trying to drag him back into the room so they would both be crushed. The eladrin made an excellent Athletics check and broke free, and one of the other PCs - the human fighter, I think - hauled him out of the lair just as the ceiling came down, burying Mogor under tons of rock. It was a hell of a conclusion.
Worst fight as a DM: I'd have to say the third fight in the very first session of my campaign, where I put a 1st-level party without a wizard up against two dire rats and three rat swarms. It was very cramped quarters - I hadn't yet learned the importance of maneuvering room in 4E - and the party lacked any effective way to fight swarms. The fighter got overwhelmed and eaten, straight from positive hit points to negative bloodied in a single round of swarm attacks. That fight was a mess.
Of course, there was also the preview session I ran with the Raiders of Oakhurst dungeon. The fight with the black dragon was godawful, just endless grinding and grinding with the players unable to make much of a dent in its hit points while it wore them down one by one. Bah.
Best fight as a player: The bridge fight Vayden described above (I was the pyromancer).
Worst fight as a player: There isn't any one fight that stands out as worst to me from the player perspective, because in 4E, the worst fights are the boring ones that slip into "grindspace," which means they're not very memorable. Some of the Keep on the Shadowfell fights were like that, as were most of the fights in our abortive "orc warriors" campaign.