The following NPC Forcegreets and Innkeeper rumors that add quests to your quest log have been disabled:

Eltrys - Markarth
Quest - The Forsworn Conspiracy
Find and talk to Eltrys to begin the quest. After he leaves the Silver-Blood Inn, he hangs around the workers in front of Cidhna Mine or sleeps in The Warrens.

Brynjolf - Riften
Quest - A Chance Arrangement (Thieves Guild)
Talk to Brynjolf in the Riften market or in The Bee and Barb if and when you are ready to begin.

Falkreath gate guards ("Did you see a dog out there?") - Falkreath
Quest - A Daedra's Best Friend
To start this quest, talk to either one of the gate guards or Lod the blacksmith.

Rumors and guard dialog about Aventus Aretino in Windhelm
Quest - Innocence Lost (Dark Brotherhood)
To start this quest, walk near Aventus' house and listen to Idesa and Grimvar's conversation or enter Aventus' house and talk to him.
I prefer to travel to Honorhall Orphanage in Riften, power-bomb Grelod, then go to Aventus' house.
New Update File: I previously missed a Windhelm Guard dialog line about the Aretino Residence, so I made a small patch. I don't want to update the Main File to a new version until I'm fairly certain I've made all of the changes I want.

*Rumors of Falion in Morthal
Quest - Rising At Dawn (Cure for vampirism)
This one probably won't work even if you talk to Falion. He doesn't seem to give any cure-related dialog options if you didn't get the quest from an innkeeper. That said, if you're a vampire, you probably became one on purpose and don't want to be cured. If you do want to be cured you can become a werewolf with the Companions or use a cure from a vampire overhaul mod. Most of them seem to include one.
*By request, I've uploaded a plugin that restores the Falion Rumors. It is in Optional Files. Make sure it overwrites the main mod.

Calcelmo/Courier - Anywhere a courier can sneak up on you. 
Quest - Buy Dwarven Artifact
This quest has been completely disabled. This is the quest that usually starts when a courier brings you a letter from Calcelmo in Markarth, after you buy a dwarven item from a merchant. I occasionally buy dwarven weapons or armor to disenchant and don't want to sell them to Calcelmo. Plus, couriers are kinda creepy. They just appear out of nowhere and waste my time.

Maul - Riften
There is no quest with this one. He just irritates me and it's illegal to punch him.

Rumors and guard dialog about the Face Sculptor - Riften Ratway
Quest - Surgery
I also disabled the Face Sculptor's forcegreet. To access her services you just need to talk to her.

Alik'r Warriors - Whiterun
Quest - In My Time Of Need
The two Alik'r in Whiterun will no longer forcegreet you and automatically assign their quest, but they will stay there until you talk to them.

Irileth - Dragonsreach
Quest - Before The Storm
Just walk right up to Balgruuf. He'll act annoyed, but she won't bother you.

Durak - Wandering Dawnguard Orc
Quest - Dawnguard
Like any truly dedicated stalker, Durak will be wandering around any cities or towns you visit, until you accept the Dawnguard quest. To start it, talk to Durak or travel to Dayspring Canyon.

New in Version 1.2

Sofie - Windhelm
Sofie is the adoptable orphan girl in Windhelm who will no longer stop you to sell her flowers.

Suvaris - Windhelm
Suvaris is  the dark elf who is being harassed by Rolff Stone-Fist and his lackey when you first enter Windhelm.

Barmaids/Tavern Servers
Barmaids across Skyrim should no longer bug you with their useless trade menu.
If they do, please message me or post which one in the comments. Things
like this are difficult to thoroughly test.

Blind Watchman - White River Watch
Now you can just walk right past him. He'll speak, but he won't stop you.

Valtheim Towers and Robber's Gorge
Both are bandit camps that try to shake you down when you approach them. Now they'll just attack. You're welcome.

Vigilant Tyranus - Abandoned House, Markarth
Quest - The House of Horrors
He'll still hang around the abandoned house until you talk to him.

Faleen - Understone Keep, Markarth
Like Irileth, Faleen is an obnoxious housecarl to a jarl. Her forcegreet was as annoying as it was unnecessary.

"Captain" Valmir - Forelhost
The door to forelhost will be locked until you either talk to Valmir or loot the key from him.

New In Version 1.3

City guard dialog related to the Dawnguard. - "Heard they're reforming the Dawnguard."
The Dawnguard quest should no longer be automatically entered into your quest log. To start it, talk to Durak when you see him wandering around or go to Dayspring Canyon.

The fugitive thief and the hunter pursuing him - Random Encounter
The fugitive is the guy who gives you some stolen piece of junk to hold for him. You will still see them at some point, but now they will just pass right by.

*Wizard Duel - Random Encounter
When you reached a high enough level in any school of magic, a pitiful little wizard would find and challenge you.
The main file only disables his forcegreet. He will still show up and stand around until you talk to him.
*By request, I've added an Optional File that completely disables this quest and the Failed Mage listed below.

Invisible Children - "Can you make me invisible?"
Joric of Morthal stopped me with his forcegreet while a group of bounty hunters were after me. After they beat the crap out of me, I decided to disable this one.

Dwemer Junk Peddlers
These are the kids in the Reach who want to sell you some junk they found at Deep Folk Crossing.

Drunken Revelers - Randon Encounter
The Honingbrew Mead enthusiasts who want you to have a drink with them.

*Failed Mage
This is a conditional encounter with a failed college applicant who wants a ward demonstration.
The main file only disables his forcegreet. He will still linger around until you deal with him.
*By request, I've added an Optional File that completely disables this quest and the Wizard Duel listed above.

Mistwatch Escapee - Random Encounter
This woman in prisoner's rags tells you that she was kidnapped by bandits and held at Mistwatch.

Bandits Dressed As Imperial Soldiers
Pretty self-explanatory, this one. Three bandits in Imperial uniforms are standing near three naked Imperial corpses. Their forcegreet was a shakedown attempt.

Madman - Solstheim
This is a wandering lunatic who spouts some nonsense, then attacks you. His forcegreet usually starts the Black Book quest.

Netch Hunters - Solstheim
Four hunters want you to help them prove their strength by killing a netch. Trust me, it is much more satisfying to hang back and watch them.

To be clear, you can still talk to these NPCs and start their quest or dialog. The only exceptions are the two quests that have been disabled (Rising At Dawn, Buy Dwarven Artifact).

If anyone has more annoying quest givers/starters, I'm all ears. Just throw them in the comments or message me.
Thanks to swhatley09, Xeron222, and psyyo for the suggestions.

Bonus Optional File:

Separate download in Optional Files. This is for fun, not immersion.

I tend to test new spells, weapons, and powers on city guards. Any time I sheath a two-handed bound weapon to use the spell in my other hand, the guards think I'm surrendering. It has always annoyed me that the resist arrest dialog option is "I'd rather die than go to prison". I've slain Alduin, dusted Harkon, wrecked Miraak, and absolutely humiliated the Ebony Windbag more times than I can remember. There is almost no chance a guard is going to kill me, so I added a somewhat more ballsy and amusing option.

The resist arrest dialog option changes from "I'd rather die than go to prison" to "Come at me, Bro".

My Other Mods

Juni - Nord Follower And Preset



Arcane Mastery



Miraleth - Bosmer Follower And Preset