Skulltula

Skulltulas are recurring enemies in the Legend of Zelda series. They are sizable spiders that exist in many dark and discreet places, such as caverns or temples, inhabited by other malevolent creatures. A mark in the shape of a skull appears on their abdomen, which seems to be an admonition all for all those who may come in contact with the creature to stay away if they wish for their own safety. When Skulltulas spot a trespasser, they attack it by dropping down from the ceiling with their web.

The Legend of Zelda: Ocarina of Time and Majora's Mask
In Ocarina of Time, the backsides of Skulltulas are vulnerable to sword strikes; they can also be defeated if Link hits one with his Hookshot or by shooting it using an arrow with his Fairy Bow. A number of Skulltulas are invisible and can be seen only by using the Lens of Truth.

In Majora's Mask, Skulltulas' front sides are invulnerable to Hookshot strikes; however, they can still be dispatched with the Hero's Bow. They are not as frequently encountered as in Ocarina of Time, and invisible ones are encountered only in a single room. However, the first regular enemy encountered in the game is a Skulltula, which appears inside the Bombers' Hideout. Unlike in Ocarina of Time, Skulltulas are able to perform a spin attack when Link approaches them.

The Legend of Zelda: Twilight Princess
Skulltulas have a different attack pattern in Twilight Princess. They attack by crawling towards Link and using a biting attack. Also, their exoskeletons offer much more protection than before. However, they can easily be dispatched by attacking their heads, either with stabs of a sword or with basic, non-jump wolf attacks. Once stunned, Skulltulas can be defeated with the Ending Blow. Once Link learns the Back Slice, it can be used to great effect against Skulltulas.

Interestingly, in an early demo at the Electronic Entertainment Expo, Skulltulas were shown to be able to tie Link up in a web and attack, but this was cut from the final product.

The Legend of Zelda: Phantom Hourglass
Skulltulas appear in the Ghost Ship dungeon. This incarnation of Skulltulas does not feature their trademark hardened shells. While they can be killed, a new one will appear instantly after a Skulltula has been defeated; a room can never fully be cleared of Skulltulas. When Link unknowingly aids the Diabolical Cubus Sisters, they appear to fear these creatures; however, it is unclear whether or not this is part of their act.

The Legend of Zelda: Spirit Tracks
Skulltulas appear within the Lost Woods in the Forest Realm, and inside the twisted tunnels of the Sand Realm. As the Spirit Train approaches, they drop down in front of the Spirit Tracks using their webs. If Link does not kill them with the cannon, or scare them away with the train whistle, the train will crash right into them and take damage. They are almost twice as big in this game as the biggest Skulltulas from Ocarina of Time, but are less frequently seen than in most games. There is also a more persistent kind that appears later on, resembling a Gold Skulltula, which will not flee at the sound of the whistle and takes two hits to kill.

The Legend of Zelda: Skyward Sword
Skulltulas appear primarily in the Skyview Temple dungeon. They can be found in webs or hanging form ceilings. If they are on the ground, Link can preform an upward slash to flip the Skulltula onto its back. This makes the Skulltulas vulnerable to Link's Ending Blow. However, if hit by Link's sword while suspended, they will twirl around on their webs and smash into Link. Proper timing though can allow for the spider's belly to be exposed to stab attacks. If Link keeps his distance from the ones on the ground, they may spit out strands of web that can tangle him simular to walking into a spider web.

Super Smash Bros. Brawl
A Skulltula from Ocarina of Time is featured as a sticker. Its sticker gives a +7 bonus to arm attacks, and can be applied to any character.

Etymology
"Skulltula" is a portmanteau of the words "skull," referring to their skull-like carapace, and "tarantula," a variety of arachnids.