Nurgle, the Chaos god of disease, decay, despair, and destruction in the Warhammer and Warhammer 40000 settings is a jovial, avuncular figure who lavishes attention on his "children" and sees himself as a creative force in the universe. He is often referred to as Grandfather Nurgle, or even Papa Nurgle. The same can be said for his mortal followers. In the fluff, you'll almost always see them joking or having a good time. At one point, after a POW gave up and agreed to worship Nurgle, his jailer just smiled and hugged him.
Also Trazyn the Infinite, a Necron lord who collects various treasures throughout the galaxy. He could not care less about conquering anything, unlike most other Necrons, and generally has the demeanor of a jovial elderly man who owns a toy store. At one point, he was attacked by a few Imperial Guard platoons. He later sent a message to their commander stating that while they put up some unnecessary resistance during the transaction, he was genuinely grateful that he received the last few specimens he needed to complete his 'Guard platoon' collection (as what he presumed were gifts).
The bread and butter of both World Of Darkness gamelines by White Wolf.
Old World Of Darkness: The Tzimisce clan from Vampire The Masquerade are generally affable towards guests in their domain. This is due to their ancient hospitality rites, which transcend even their love of recreational torture and desire to turn everything fleshy into living, tortured abominations. A perfect example is Andrei, a Fiend from Vampire: The Masquerade - Bloodlines, who openly, calmly, and truthfully converses with the Player (unless they're Tremere) when they first meet in his mansion decorated by human flesh...
New World Of Darkness: This is especially common in the Vampire The Requiem gameline. Since vampires are evil within the context of mundane human in-game morality, they do what they can to prevent themselves from appearing evil. The Ventrue and the Daeva clans, particularly, thrive on this trope, even going so far as to have an active rivalry between each other as to which style of manipulation (Honey vs. Vinegar) is superior. Unlike their Masquerade counterparts, the Nosferatu of Requiem can also handily play within this trope, and can even outdo their classier and prettier opponents.
In the Mekhet clanbook, Frances is funny, sweet, apologetic, and into indie music. She also brainwashes a house full of female students so she can feed on them, turns her boyfriend into her devoted ghoul ("I think I've broken him"), and toys with a female executive before killing her in the most humiliating way possible.
Forgotten Realms has Sshamath — technically, it's an evil drow magocracy, and they didn't disown Lolth, having only thrown off the theocracy. But for the sake of trade, it was made as pleasant as a drow city could be. This includes restrictions on slavery and having one of the best taverns catering to any sentient being (with special floors for freshwater, saltwater, and flame-dwelling clients).
Dragonlance: Some of the Krynnish evil deities can be very friendly when they want to be. Sargonnas really does care about his followers, and has standards and a sense of honor. Nuitari can get along well with Solinari and Lunitari, due to the three deities representing Evil, Good, and Neutral magic. He also can get along fairly well with mortals. Chemosh, the God of Undead, is apparently capable of caring enough for another being that he can feel genuine grief when that being is hurt. Zeboim, the Goddess of Storms, really does care for her son. In terms of mortals, the Black Robes frequently come across as being rather nice (Dalamar and Iolanthe) and are able to get along with their White and Red Robed fellow Wizards.
Pathfinder: Laori Vaus. Dear Zon-Kuthon, Laori Vaus. She's a friendly, upbeat allied NPC cleric in the Curse of the Crimson Throne module, who happens to be a devout follower of the god of darkness, pain, and loss (and not in a Dark Is Not Evil way, either). She's one of the more popularPathfinder NPCs.
Nobilis: Hell sincerely loves you, and everything else in existence, but has spent so long focusing its love on the corrupt and malignant that there's been a degree of cross-contamination. The Excrucians can also come across as charming and caring yet a horrifying threat to all of existence.
Exalted: The ideal for Moonshadow Caste Abyssals is to be an approachable, sociable diplomat for the faction that wants to drag all of Creation into the Void at the bottom of the Underworld. But really, anyone with high social skills and goals that are opposed to yours can come across as this.
