I’ve always loved making characters in D&D that have race and class combinations that are not only have racial traits that support or boost class features (either bonuses to key abilities score for said class or other racial traits like skill bonus to class skills for example) and fit well with the lore for the race, class, and/or setting.
Both Sorcerers and Warlocks in 5th edition absolutely rule in this regard, with each of their Sorcerous Origins (either a bloodline interbred with magical creatures or unusual magic circumstances of your birth) and Otherworldly Patrons (magical entities close to godlike power that are the source of your magical abilities) having a race that fits together in a perfect pairing. Here are some examples;

Warlocks
Official Sources (Player’s Handbook, Sword Coast Adventurer’s Guide, Xanathar’s Guide to Everything)
Patron: Archfey, Race: Firbolg
Other Fey related races like the Elf (Eladrin) and Centaur make alternate choices.
Patron: Celestial, Race: Aasimar (any subrace)
A race descended from and guided by Angels having their prayers for aid answered by an Archangel Patron granting more celestial power.
Patron: Fiend, Race: Tiefling (any subrace except Abyssal)
A race descended from Devils tricking, stealing, or bartering for more diabolic magic from their Archdevil forebears.
Patron: Great Old One, Race: Verdan
A race of Golinoids mutated by an entity only known as That-Which-Endures, some are able to draw further power from this ineffable unknown.
Patron: Hexblade, Race: Elf (Shadar-kai)
A race of Elves native to the Shadowfell linking their souls a Shadowfell entity that manifest in sentient weapons like the infamous Blackrazor. Very reminiscent of Elric of Melnibone.
Patron: Undying, Race: Vampire (either subrace)
A fairly low powered Vampire from the either the planes of Ixalan or Zendikar bonding with a more powerful undead like the Vampire Lord Count Strahd or the Demi-Lich Acererak. Very reminiscent of Alucard from Castlevania.
Playtest Content (Unearthed Arcana, Plane Shift, Twitch Stream, Twitter)
Patron: Ghost in the Machine, Race: Warforged (any subrace)
A living humanoid machine granted technology based magic by an all powerful A.I.
Patron: Lolth, Race: Elf (Drow)
By drawing power directly from their demon-goddess in exchange for a price one pales to consider, these Drow enhance their innate magical talents and are able to take on Lolth’s favored form, a giant spider.
Patron: Lurker in the Deep, Race: Triton
Race from the Elemental Plane of Water making pacts with the ancient Primordial Elementals dwell in furthest depths of that endless ocean.
Patron: Noble Genie, Race: Genasi (Any)
Deepening your inborn connection to geniekind, you make a pact with one of it's rulers. Offering fealty and servitude in exchange for knowing more about your origins.
Patron: Raven Queen, Race: Human (Revenant)
Having meet an undeserved end you find yourself returned to the realm of the living with a raven familiar and strange new powers. Did the Raven Queen take pity on you? A question for another time, for now there are wrongs that must be set right before you can know rest. Very reminiscent of Eric Draven from The Crow.
Patron: Seeker, Race: Gith (Githzerai)
A native to the Astral Plane drawing magical power from knowledge seeking entities that wander said plane.

Sorcerers
Official Sources (Player’s Handbook, Sword Coast Adventurer’s Guide, Xanathar’s Guide to Everything)
Origin: Divine Soul, Race: Aasimar (Any)
Angelic ancestry manifesting as celestial magic since birth and only growing stronger.
Origin: Draconic, Race: Dragonborn
The selection of both Draconic Ancestors could represent a pure bloodline blossoming to greater power or a mixture or dragon species creating a sum greater than its parts.
Origin: Shadow, Race: Elf (Shadar-kai)
The obvious links between Shadar-kai and Shadowfell magic aside, Revenants and Vampires would mesh well with the undead-like abilities in the Origin.
Origin: Storm, Race: Genasi (Air)
Djinni ancestry manifesting as auran magic since birth and only growing stronger.
Origin: Wild, Race: Tiefling (Abyssal)
The raw chaos of the Abyss courses in your veins making your magic unpredictable to everyone even yourself.
Playtest Content (Unearthed Arcana, Plane Shift, Twitch Stream, Twitter)
Origin: Aberrant, Mind Race: Simic Hybrid
Either you were mutated by strange energies from the Far Realm or experimented on by an Aberration like the Aboleths or Illithids.
Origin: Clockwork Soul, Race: Warforged
Artificial Humanoid exposed to the mechanical magic from the plane of order.
Origin: Giant Soul, Race: Goliath
Goliaths have a natural enmity towards Giants. Some tribes might have a totemic relationship with the Giant species they prefer to hunt and raid, showing a spiritual reverence to their bitter enemies for being worthy foes. And in one of those tribes you were born with a connection to that Giant totem.
Origin: Phoenix, Race: Any (Revenant)
The fiery power of a Phoenix burns within you, granting you immolating magic and the inability to stay dead.
Origin: Pyromancer, Race: Genasi (Fire)
Efreeti ancestry manifesting as ignan magic since birth and only growing stronger.
Origin: Sea, Race: Genasi (Water)
Marid ancestry manifesting as aquan magic since birth and only growing stronger.
Origin: Stone, Race: Genasi (Earth)
Dao ancestry manifesting as terran magic since birth and only growing stronger.

This also gives me some great ideas for some truly incredible (both in terms of ability or background) for multiclass or gestalt Sorcerer/Warlocks.
Origin: Aberrant Mind Patron: Great Old One Race: Simic Hybrid
After being experimented on by creatures from the far realm or mutated by in otherworldly energies, you have turned to the strange alien god-like entities that hail from that distant plane to further augment your pseudonatural abilities. 
Origin: Clockwork Soul Patron: Ghost in the Machine Race: Warforged
it's the inborn magic of his mechanical nature expanded upon contact with Mechanicus, soon sought out a powerful AI to bargain for moe technological power.
Origin: Divine Soul Patron: Celestial Race: Aasimar
Combing angelic heritage strong enough to manifest sorcerous magic and Aasimar traits, you forge a pact with a powerful Solar. Now you wield divine healing and radiant energy enough to make most clerics and paladin envious. 
Origin: Sea Patron: Lurker in the Deep Race: Genasi (Water)
Born of raw elemental fury of the Plane of Water, your connection to a fundamental pillar of creation fuels you sorcery. Your magical potential has drawn the attention of a Primordial Water Elemental. Becoming more of a force of nature than ever before, your enemies have sown the tide, now time for them to reap the tsunami. 
Origin: Shadow Patron: Hexblade Race: Elf (Shadar-kai) A champion of the Raven Queen, you wield fell powers over darkness and death. Absorbing the shadows and negative energy into your very very essence, you have found kinship with the sentient sword made of pure darkness; Blackrazor.