Tyki Mikk (D.Gray-man), in his awakened state, can extend many tentacles.
Killer B's (Naruto) Partial Transformation.
Dr. Octopus (Spider-Man 2)
Uroboros injection (Resident Evil)
William Birkin (Resident Evil)
The Thing Monster (John Carpenter's The Thing)
Las Plagas (Resident Evi)
She-Venom (Marvel Comics)
Gelt (Marvel Comics) is a Deviant with the power to sprout tentacles from where is arms are located.
James Heller (Prototype 2) using his tendrils.
Solidus Snake's (Metal Gear Solid 2: Sons of Liberty) exoskeleton comes equipped with "Snake Arms" that can strangle opponents and fire missiles.
Ultimate Spider-Man (Spider-Man: Shattered Dimensions)
The Shadow Blot (Epic Mickey)
Dark Gaia (Sonic Unleashed)
Nemesis's (Resident Evil) tentacles are sharp enough to penetrate human flesh and bone.
The Nemesis T-Type (Resident Evil) attacks Jill with a tentacle.
Alexia Ashford (Resident Evil)
The Elder God (Legacy of Kain) is little more than an amorphous mass of tentacles and eyes, the former of which it uses offensively to great effect.
The Dahaka (Prince of Persia: Warrior Within)
Laughing Octopus (Metal Gear Solid 4: Guns of the Patriots)
Doctor Octopus 2099 (Spider-Man: Shattered Dimensions)
Omega Red (Marvel Comics) uses his carbonadium tentacles to great effect.
The fake Groudon (Pokemon: Jirachi Wish Maker)
Kagura (InuYasha) impaled on Naraku's tentacles.
In their human form, Inkling's (Splatoon) "hair" is six of their tentacles from their squid form.
The Squid Sisters (Splatoon), Callie (left) and Marie (right)
Cap'n Cuttlefish (Splatoon)
DJ Octavio (Splatoon), like all Octarians, possesses tentacles.
Annie (Splatoon), being a sea anemone, has tentacles for hair.
Jelonzo (Splatoon), being a jellyfish, has tentacles.
Coldsteel (Gargoyles) uses robotic tentacles in his arms.
Abyss the Squid (Archie's Sonic the Hedgehog)
Fused with the Ghost ÄRM, Hydra, Chimera (Marchen Awakens Romance) can generate sharp tentacles from the demon's body.
Kaneki Ken (Tokyo Ghoul) can generate tentacles via his Rinkaku-type kagune.
Maji Kayo (Dragon Ball Super) using tentacles to restrain Goku.
Vampires (JoJo's Bizarre Adventure) drain blood from their victims using retractable tentacles in their fingers.
Dio Brando (JoJo's Bizarre Adventure Part I Phantom Blood) extending tentacles from his severed neck to attack Jonathan Joestar...
...and to reattach his severed arm.
Thresher, A.K.A. Experiment 544 (Lilo & Stitch)
Agent Venom (Marvel Comics)
Jimon's (Samurái Deeper Kyo) Kenyou form.
Anti-Venom (Marvel Comics)
Priscilla (Claymore) extending her fingers into tentacles to impale her enemies.
So'unga (InuYasha) sprouts multiple tentacles from itself to anchor Inuyasha's hand to it.
SCP-058 - Heart of Darkness (SCP Foundation) has several tentacles protruding from the top.
Slender Mann (TF2 Freak) can sprout tentacles from either his back, or also from his hands. The tentacles are also strong enough to dismember people with little effort alone.
The Centauri (Babylon 5) possess six tentacles on their sides that double as their genitals.
Meat Sweats (Rise of the Teenage Mutant Ninja Turtles) possesses tentacles in place of hands that he can use to drain energy and powers from other mutants.
Dahaka (Prince of Persia: Warrior Within)
Kevin 11,000 (Ben 10) possesses Null Guardian's tentacles.