Playing my dual-wielding dervish, and had a radiant mission to kill a giant. Pretty normal. I attacked the giant, but it was night and I hadn't noticed that there were two giants sitting there. So suddently I'm fighting both. Then two mammoths joined in (I had seen the mammoths but they were far away from the original giant. The second giant must have chain-pulled them). At this point I sort of resigned myself to reloading from a quicksave, but figured I'd give it my all just to see how far I got.
Now, this is the unbelievable part, but I promise it's true. Fast traveling to the camp must have spawned a dragon, but I never noticed until suddenly, amidst the giants and mammoths, I'm also being hit by frost-breath. Obviously it's impossible to switch to bow and shoot at the dragon as long as the giants and mammoths are alive, so I'm running around like crazy trying to focus on at least one of the things while avoiding the other four. Three wolves have joined in too. Not that they were dangerous at all, but they did contribute three extra red dots so I have no idea where anything was.
I actually managed to come through that fight without having to reload. Entirely with William Wallace style strike-hard-then-run-like-hell tactics. I only got hit a couple times (not counting dragon breath) but each took me ALMOST to dead. I didn't have enough potions to handle a third hit, so that would have been the end.