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)
Caustic (Apex Legends)
Wiggler ("Super Mario series")
Super-Soldier Serum (Marvel Comics)
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, but not including Armored Stonefish.
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, including Armored Stonefish that can kill Giants and even the poison-resistant Monkey D. Luffy.
Bianchi (Reborn) is able to eat her own poisoned cooking without ill effect and believes the poison enhances her cooking.
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.
As they are Lich Zombies, Fork Maidens (New Blood Interactive's DUSK) are immune to poisons, especially if they were to go up against a select group of users that have powers related to poisons.
As they are immune to all sorts of contaminative substances, the Possessed Scarecrows (New Blood Interactive's DUSK) cannot be harmed by poisons.
As robotic defense guns, the Turrets (New Blood Interactive's DUSK) are immune to various poisons.
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, becoming the Scorpion King and immune to poison.
Snorlax (Pokemon) may have the ability "Immunity", granting it immunity from poison.
Due to being magically constructed out of the air by Mental, the Air Elementals (Serious Sam) are all impervious to poisons, in addition to being a substitute ability of their immunity to various contaminants.
Built from solid ice, Ice Elementals (Serious Sam) are impervious to all sorts of poisons.
Stone Elementals (Serious Sam) are immune to all kinds of poisons due to their mineral physiology.
The Water Elementals (Serious Sam) are impervious to all kinds of poisons due to their watery physiology.
Through extensive experimentation and expertise, Caustic (Apex Legends) knows how to adapt in and around poisonous gas.
Thanks to the Permanent Effect: Longevity, Sung Jin-Woo (Solo Leveling) is immune to all forms of diseases, poisonous substances, and any other abnormalities.
Alejandro (Heroes) is immune to his sister's Poison.