Over the past few years I've been teaching my son to play D&D. We started with Lost Mines of Phandelver in the starter set. Now he's hooked and we are branching out. Regardless, We had a party of 4. My son and his friend were both mages and my wife played the cleric/tank. I played a DMPC ranger. The group snuck into Craigmaw castle through the side entrance and managed to avoid any contact with rebrands until they accidentally entered the dining hall (Room 7) during meal time. It's a shame they forgot to make a listen check before marging in! The room was packed with almost a dozen rebrands and the head cook serving from a cast iron skillet. My team, astute as always, did not remember to don their red cloaks from Tressendor Manor. After a failed attempt at deception the chef attacked them with the cast iron while the rebrands all drew small weapons from their belts and boots. The team took out the chef who fell in front of the door they entered through; blocking their retreat. Soon pounding was heard on the other side of the door, but the chef's body blocked the reinforcements' entry, too. The cleric deflected attacks to the mages who struck out with magic missile and grease, respectively. Several rebrands went down. The ranger made a great acrobatics check and vaulted to the top of one table where he defended against numerous attacks with Hew, the magic Battleaxe. In an astonishing display of single-minded determination, the rebrands were so confident in their eventual success that they never broke ranks. Though one door to the dining room was blocked, the reinforcements looped around and entered in via the North entrance. At one point, they even managed to clog the entrance by failing to navigate the press of their comrades and the bodies on the floor. The rolls were in favor of the players that night as they used flaming hands to great effect to subdue several rebrands at a time. When the dust settled, my team was nearly out of spells and low on HP, but survived to see the doppelgänger fleeing the castle after delivering a near-fatal wound to his dwarven captive. 

That sounds utterly awesome, would kill to run a combat like that :)

Furthermore, my fave combat would most likely be a certain battle against a beholder. For context, the players were all level eight, consisting of a tabaxi ranger/fighter, a drow assassin, a firbolg storm cleric, and a lizardfolk fighter, and with a NPC dignitary using the nobleman statblock that they were protecting, having rescued from kobold a few sessions back. Ranged against them were three thugs, an enchanter, and a full on beholder named Barasikks The Hideously Wonderful.

It started out well, with two of the three thugs being killed before they got an action by the tempest cleric, who blasted them apart with lightning and then used spiritual weapon to kill the enchanter before he could fireball the party, since the rogue had sneak attacked him and rolled a critical hit. Then the Barasikks’s turn came. She disintegrated the NPC instantaneously, and successfully Fear-rayed the rogue, preventing him from getting into combat with it, and finally used its petrification ray to stop the cleric from doing anything. 
For the rest of the fight the three remaining adventurers (the cleric got turned to stone) where all being fear rayed on and off, the fighters armour was partially disintegrated by another eye ray, and the telekinetic rays flung them all over the over the place into walls and rocks. The fighter eventually perished to the death ray, and the ranger was charmed by the beholder and started killing the rogue before the beholder Deemed him no longer a threat and telekinetic-rayed him into a Boulder, dealing 3d6 damage and breaking his neck, before causing him to fail his death saves by eating the body while the rogue hid. The rogue charged the wounded beholder (the rogue and ranger had been best of friends since childhood) and stabbed the beholder in the side, getting it down to one hit point, before it blasted him away with its eye rays, specifically the sleep ray. 
Groans from the players as they realise that the fight has been lost, and the beholder’s ragtag army of mercenaries will destroy the world they they’ve been working for so long to protect. Then one voice speaks up.
The rogue’s player raises his voice.
“I can’t be put to sleep with magic.”
The table explodes, everyone screaming and hollering in amazement as the battered drow grabs his notched blade from the cavern floor and stabs it through the beholder’s central eye with a howl of anger. And then, as the screaming, thrashing monster finally lies still, he picks up a stretcher from now-empty the war camp. Puts the mangled bodies and statues of his friends upon it, and leaves the cave, heading for a new dawn.

This was only our third in-person game and man was it a good one.