The Seraphim resembles Angela from Spawn in design (most notably Excessive Evil Eyeshadow), concept, and even personality. According to Word of God, FX developer Steve Manekeller was directly inspired on Angela, though his coworker Michael Bhatty also based her on the paladins from David Eddings's The Elenium.
The Dark Elf resembles DrizztDo'Urden quite a bit, although he seems to have started out a bit more villainous.
His backstory, and training as an assassin, also make him similar to Khainite Assassins from Warhammer Fantasy, especially seeing he was a member of the "Blood Cult" (that is also a death cult), sounding very similar to the cult of the Khaine, the Bloody-Handed God.
Shaddar echoes Borbarad from The Dark Eye. Although it's complicated, as Sacred did start out as an adaptation of The Dark Eye, and apparently Shaddar originally was one of Borbarad's apprentice, who wanted to continue his legacy.
One of the quests involves a forest ranger named "Arogarn", who is resting in an inn. He has the same outfit as Aragorn when the Hobbits meet him for the first time. There are further rangers in the game named after almost every possible variation of "Aragorn".
The underground tavern under Braverock Castle is named "Ascaron's Call", an obvious pun about fellow Cult Classic RPG Asheron's Call, which was released a year before Sacred.
A little town in the game is an accurate copy of Tristram. If the player wanders a bit in it, all inhabitants turn into zombies and attack him/her.
There's a secret location near Drakenden based on Camp Crystal Lake, where the player can find Jason Voorhees's mask and machete. Only the Gladiator can use them, though.
Underworld has an underground location in the Dryad Forest where a Shadow Vessel from Babylon 5 can be found. It has the ability to insta-kill the player with a quick laser, though.
In a quest in the Gold edition, the player has to help a pirate named Jak Arrow to dispose of some undead pirates. Now that's subtle.
The island of Mal-Orc-A references Germany's favorite holiday island Mallorca. The "6" on the ground near the Seraphim barmaids refers to the infamous Balneario "Ballermann" 6, which is favored by binge tourists. A quest there requires you to walk all over the orcs' beach towels until they attack you. Kill them and you are awarded designer sunglasses.
The Shadow Warrior is basically Guts from Berserk. Not only because his ears, face, physique and some of the black armors and big swords he shows in promotional images◊ make him resemble the Black Swordsman himself, but also because, very much like Guts, the Shadow Warrior is a fighter with a dark past who is now living in an "interstice" between the physical plane and the spirit world and has gained some skills thanks to it. Ironically, while Guts is constantly fighting off skeletons and undead creatures, the Shadow Warrior actually controls them.
The High Elf's Shadow Path design resembles quite much DrowPriestesses.
Also, Her Shadow Path design/Pearl Set is alternatelly reminiscent in look to a Dark Elf Sorceress from Warhammer Fantasy.
With his dark cloak, deep voice, wizened face, lightning techniques and membership of a dark order, the Inquisitor is the Sacred version of Darth Sidious from Star Wars.
He has also many allusions to Darth Vader. In fact, one of the additions of the Community Patch is Vader's helmet as an unique helmet for the Inquisitor.
Gladiator's armor set wouldn't be out of place in the ranks of the Chaos Warriors.
