I was recently in Windhelm talking with the blacksmith when I heard a ruckus coming from the main gate. Thinking it was Serana starting some trouble, I went to investigate and got sideswiped by a rampaging Gargoyle! lol
It took my by such surprise that I needed a moment to process what the hell was going on. Turns out 2 lesser vamps + 1 Ancient Vamp + 1 Volkihar Vamp + 1 conjured Gargoyle had suddenly entered the front gate. Guards and various citizens ran into the fray. Arrows flew back and forth, frost spears and lightening bolts crashing all around, people yelling, cries of terror when a few citizens had sense enough to duck and run. It was all so exciting!
Then I noticed that Serana was grabbing everyone's attention like the good little tank she is, so I pulled out Auriel's Bow and started burning them down. After I dropped the Ancient and worked the Volkihar to less than half hp, I rushed the remaining lesser vamp shooting arrows at me and impaled him on my daggers >D
In the end, the only loss was the blacksmith girl and a couple of guards. I had already completed her quests so I was tempted to just leave it as is....but I kinda like the banter between she and the older smith-guy. So I had to reload it. My reload went smooth and the attack never came! so she's still alive in my game.
I'm not bitter about it at all. That was likely the most fun I've unexpectedly had in days!

Had I not been trying to get Windhelm's house and Thane title, I would have gone Vampire Lord and everyone would have died!