- "Zilla sends his regards."
- —Evil Ninja at the start of Shadow Warrior Classic.
Evil Ninjas are the most common enemy type in the game. They come in five different variations:
Red - Will do everything his brown cousin does, plus he can shoot small rockets at you, as well as shoot Uzis. This variant doesn't use shurikens.
Shadow - The most fearsome of the lot, this ninja uses the ancient skills to stay nearly invisible. He can blast you with two type of magic napalm, one being a wall of fire. Beware, because this ninja is also skilled in use of the flash bomb. Once blinded, you will have little chance of survival.
Orange - These ninjas have added ability to shoot heat seeking rockets at you. Very nasty in open areas. After death, they sometimes drop a heat seeking card.
Gray - These ninjas have been upgraded with the ability to launch grenades at you. Considering the blast radius of grenades, these guys are particularly nasty. After death, they can drop grenades.
Mercenaries - Appear in Wanton Destruction expansion. Act exactly like Evil Ninjas counterparts, except have different visual design. The color of their hats reveal what kind of variation mercenary is.
Evil Ninjas have muscular body. They only wear pants which differ in color depending on ninja type. Their hair are tied in a ponytail. They eyes glow bright red and mouth is full of pointy teeth. Shadow variant is exactly the same except is entirely in black. Mercenary variation has entirely different design, wearing black tuxedo, with sunglasses and a brown hat. Another unique design part is their mustaches.
- Brown Ninjas are the easiest to deal with; they can be chopped up in one katana strike and their shurikens deal little damage;
- Orange and Red ones are more dangerous because of their ability to shoot rockets, the latter firing homing missiles. When fighting them, it is best to take distance as to anticipate and notice when Orange and Red shoot their rockets at you. The same goes for Gray Ninjas. The danger in these enemies is the killer and immediate damage they'll deal to you if up close; always keep your distance.
- Shadow Ninjas are the most dangerous of the bunch. They can easily blend in the surroundings, and be hard to see even when running wildly about. He shoots two variants of Guardian's Head fireballs: one fireball which shoots smaller shots as it goes, and one consecutive fiery blasts forward. The Shadow Ninja is especially lethal thanks to his restrain from shooting his Uzi at you, "revealing" himself only to fire this second variant of fireball, which deals deadly amount of damage. Terminate them with extreme prejudice; a good way to soften them is to disengage and throw a Gas Grenade or sticky bombs at their location, returning after damage has been dealt.
- Tough they are called "Ninjas" in the game, aesthetically they look nothing like ninjas or anything even resembling a human.
- Evil Ninja is the only regular enemy that can be heard speaking in Shadow Warrior Classic.