I decided to do something nice for Ulfric Stormcloak, since he'd given me a nice new suit of Stormcloak armor and a number of missions where I got to carve up legions of the hated Imperials. So I asked his assistant if there was any work that the community needed done - and he gave me the task of exterminating a giant.
By this point I'd gotten close to exactly one giant, an incident which directly inspired my long-standing policy of hauling ass in the opposite direction at the first sight of a club-wielding silhouette on the horizon. I was not looking forward to this fight.
But anything for the Stormcloaks, so I snuck over to the nearby giant camp where, sure enough, something abnormally large was lumbering about, club on shoulder. I decided to inflict as much damage as possible right away, so I equipped my best arrow, laced it with my most expensive poison, and made absolutely sure I was undetected.
As soon as the giant stumbled into my sights, I let the arrow fly, hitting the giant with the full Sneak Attack bonus plus poison damage. The giant spotted me immediately, and came charging at me with barely a dent in his health meter. And THAT'S when I noticed that he wasn't alone.
Out from behind that big stone pillar with a mammoth skull on top, came ANOTHER giant, also pissed off. The newcomer had a full health meter - and a big, conspicious white map indicator shining over his head.
Yup. I had messed with the wrong giant.
While I was busy being astonished, giant #1 was able to score his first hit, a single sweep of his club shaving off half of my health meter. I turned tail (literally, I play a Khajiit) and ran down the hill. Another hit took out nearly all my remaining health, I hit the Inventory button and guzzled a massive amount of those weak-ass health potions I'd been finding everywhere.
Giving up any hope of escape, it dawned on me that my best bet was to give up on my Stormcloak ambitions and just hope for a calm, uneventful career as a rug in whatever distant part of Skyrim I'd shortly find myself. I decided to go down fighting, though. I pulled out my trusty scimitar and started whacking away at the giants.
Amazingly, though the giants had soon trimmed my health bar back to almost nothing, I remained firmly footed in the Windhelm area. I opened my inventory again to look for more health potions, and spotted something I'd forgotten that I owned: A Dwarven sword with a nice Absorb Health enchantment! I didn't equip it when I got it because I wanted to save it for emergencies.
I drained another crapload of potions, grabbed the Dwarven sword, and started whacking away at the giants. Eventually, to my surprise, they both dropped dead. I harvested their filthy toes, reported back to Windhelm, and secretly wowed never again to seek gainful employment.