Due to his prolonged exposure to it, Scarecrow (Batman: Arkham Knight) has built up a partial immunity to his own fear toxin, though he was still affected when Batman injected him with several vials of it.
As a dhampir, Rayne (BloodRayne) is more resistant to sunlight and water than pure vampires.
Due to his advanced age and strength, Angel (Buffy the Vampire Slayer) has a higher resistance to sunlight and holy items than most vampires.
Due to his advanced age and strength, Spike (Buffy the Vampire Slayer) has a higher resistance to sunlight and holy water than most vampires.
As a human-Kryptonian hybrid, Superboy (DC Comics) is more resistant to Kryptonite than pureblood Kryptonians.
Kain (Legacy of Kain) possesses an immunity to certain forms of water, such as rain and snow, but cannot survive being immersed in large bodies of it.
The enhanced Type 2 Las Plagas (Resident Evil) are resistant to sunlight and other forms of bright light, though very intense light, such as flash grenades, still harms them.
Due to his Regenerative Healing Factor, Wolverine (Marvel Comics) is highly resistant to diseases, drugs, and toxins, though he can still suffer the immediate effects of such substances in massive quantities.
Due to his Accelerated Metabolism, Spider-Man (Marvel Comics) has a higher tolerance to such things as drugs and poisons than a normal human.
Repeated exposure to sonic vibrations has allowed Venom (Marvel Comics) to build up a tolerance to them...