Banshees (Teen Wolf); magical, such as Kanima's neurotoxin
Isabel (A Fierce and Subtle Poison)
Zombies (Hλlf-Life series)
The Courier (Fallout: New Vegas); via Heartless perk
Fire Elementals (Crypt of the NecroDancer)
Golems (Crypt of the NecroDancer)
Ice Elementals (Crypt of the NecroDancer)
Mushrooms (Crypt of the NecroDancer)
Skeletons (Crypt of the NecroDancer)
Slimes (Crypt of the NecroDancer)
Zombies (Crypt of the NecroDancer)
Sliths (Unreal series)
Suu (Monster Musume)
Black Ops Psionic Amplifier/Psi Amp (System Shock 2)
Toxin Suit (Unreal series)
Sōsuke Aizen's (Bleach) tremendous regeneration powers gained from the Hogyoku allowed him to survive the deadly poison of the Kamishinino Yari.
After training with Orochimaru, Sasuke Uchiha (Naruto) developed resistance and immunity to various poisons.
With the power of the Doku Doku no Mi, Magellan (One Piece) is immune to all poisons, including his own.
After surviving his encounter with Magellan, Monkey D. Luffy (One Piece) gained anti-bodies that make him resistant to various poisonous substances.
The Gasu Gasu no Mi made Caesar Clown (One Piece) immune to poisonous gases.
Vinsmoke Reiju (One Piece) has complete immunity to the deadliest venom that can kill Giants and even Luffy.
Bianchi (Reborn) is able to eat her own poisoned cooking without ill effect and believes the poison enhances her cooking.
Wolverine's (Marvel Comics) Healing Factor protects him from poison, including the metallic poisoning from the Adamantium that is stored in his body.
The Flash Bees (My Little Pony: Friendship is Magic) are highly immune to swamp fever.
Poison Ivy (DC Comics) is immune to all forms of poisons/toxins.
Suu (Monster Musume) can consume any foods that could result in food poisoning to both Humans and Extraspecies, and even discerning what's poisonous and what isn't. The only side effects being that she gets more abrasive after eating poison.
The Zoldyck Family members (Hunter X Hunter) are trained to resist all kinds of poison.
Mathayus/Scorpion King (The Mummy Returns/The Scorpion) bartered his soul to Anubis, becaming the Scorpion King and immune to poison.
Snorlax (Pokemon) may have the ability "Immunity", granting it immunity from poison.