Ultraman Hikari (Ultraman) via fusion with Ultraman Mebius
Ultraman Zero (Ultraman)
Darkliptor (Power Rangers in Space)
Giga Guirail (Denji Sentai Megaranger)
Ultimate Org Senki (Hyakujuu Sentai Gaoranger)
Various Giant Robos (Super Sentai/Power Rangers)
Riders (Kamen Rider)
Vampy Cats/The Swell (Buffy the Vampire Slayer Season Eight)
Kumiko Ishihara (Buffy the Vampire Slayer Season Eight)
Legion (Red Dwarf)
Tuvix (Star Trek: Voyager)
Rin Kaenbyou (Touhou Project); a cat youkai, who actively turns into her cat form (most youkai in Touhou are humanoid)
Alecto (God of War)
Remilia Scarlet and Flandre Scarlet (Touhou Project); as vampires able to turn into bats. Remilia is able to turn into an entire swarm of bats, and is able to recover from just one.
Keine Kamishirasawa (Touhou Project); able to transform in a were-hakutaku during full moon.
Chaos (Sonic Adventure); has animal forms when in possession of 4 and 6 of the Chaos Emeralds - a shark and a giant insect. In addition, Perfect Chaos - which uses the energy of all 7 of the Emeralds - is a huge lizard. All the animals are identified as different from regular ones by being made of water.
Nidalee (League of Legends); Can turn into a large feline - the exact species of which depends on what skin is in use at the time. Her default skin has her turn into a cougar. Being in feline form gives her a different set of skills to normal.
Druid Class (Diablo II: Lord Of Destruction / World of Warcraft)
Druid Class (Warcraft)
Eidolons (Final Fantasy XIII)
Shadow Bugs (Super Smash Bros. Brawl)
Bowletta (Mario & Luigi: Superstar Saga)
Bellumbeck (The Legend of Zelda: Phantom Hourglass)
Joseph Bertrand III (Infamous 2)
The Beast/John White (Infamous)
Mario (Super Mario)
Luigi (Super Mario)
Yoshi (Super Mario)
Ganondorf (The Legend of Zelda)
Terra-Xehanort (Kingdom Hearts)
Sora (Kingdom Hearts); via drive forms.
Riku (Kingdom Hearts); via dark mode.
Various Keyblade Wielders (Kingdom Hearts)
Nanosuit Users (Crysis)
Alex Mercer (Prototype); via shapeshifting powers
James Heller (Prototype 2); via shapeshifting powers
Ventus-Vanitas (Kingdom Hearts Birth by Sleep)
Shadic (Sonic the Hedgehog: Nazo Unleashed)
Ermac (Mortal Kombat)
Asura (Asura's Wrath)
Wyzen (Asura's Wrath)
Atrocity (Spider-Man: Edge of Time)
Queen Plaga (Resident Evil 4)
Mega-Mix (Crash Bandicoot: The HUGE Adventure)
Dark Kahn (Mortal Kombat vs. DC Universe)
Users of the Chaos Emeralds (Sonic The Hedgehog series)