Oh, funny you'd ask. I have a pretty big black list, myself.
1- The one I hate the most is a kid (what a surprise!) in Solitude. It's the blacksmith's son, I don't remember his name, but he ALWAYS says "I thought adventurers were supposed to look tough." Bi**h please, I'm wearing full Daedric armor. I don't LOOK tough, I AM tough. "I bet my papa could beat you up." OH YEAH? I'D LIKE TO SEE HIM TRY, YOU LITTLE S*IT! I've defeated Alduin the World-Eater, Lord Harkon, the Thalmor, Miraak and the Imperial Legion, your lazy-ass dad is nothing to me.
Damn, I tried to kill this brat's dad just to shove it in his face, but unfortunately the bastard is essential... The only kids I don't find annoying are Mila Valentia, Lars Battle-Born, Babette (not technically a kid but meh) and that girl in Riverwood, forgot her name. I can't believe almost no one mentions this little cr*p, I can't stand him.
2-Delphine. No, it's not only because of Paarthurnax, I already despised her long before that. It's the way she is, being rude to you from the beginning, treating you like a servant, when ironically, SHE'S the one who should be serving YOU, since you're the Dragonborn and she's a Blade. The Paarthurnax thing was just the icing on the cake. I would have killed her long ago if I could, unfortunately I play on consoles. I still shouted her off of the Sky-Haven Temple's courtyard, though.
I have no problem with Esbern, but Delphine just gets on my nerves.
3- Nazeem and Heimskr have been dead for a loooong time. Sigurd is more than probably the next.
4- The Vigilants of Stendarr. Being a Daedra Worshipper and a Werewolf myself, and having vampire friends, I obviously despise these puffed-up a-holes. They act so tough and think they can beat any Daedric Lord on existance, but they carry steel swords. They don't even have an armor themselves, they just use default mage robes. What a bunch of arrogant losers. I don't like arrogant as*-hats who pretend they are more than what they can be.
Naturally, I wiped them all away from Mundus. Their halls lie desecrated and they're all dead. I'd do more if I could, believe me. These aren't just annoying for me, they're demons. I absolutely ABHOR them.
5- That Imperial bi*ch Captain at the beginning of the game. I follow Ralof into the keep every single time just so I can get back at her.
6- Finally, every single Thalmor there is (except from the one in the College. I actually like that guy.) The worst of them is Ondolemar, by far.