Elemental Barrier

A Sub-Trope of Instant Armor and Sister Trope of Elemental Armor, this trope utilizes elemental forces as a form of (instantaneous) protection in a shape of a usually spherical barrier that covers the user. It can be a ball of flame, sand, lightning, or any elemental manifestation.

See Instant Armor for worn armor that appears instantaneously and Elemental Armor for an elemental variation of the former.

Anime and Manga

 * Gaara from Naruto has, outside from his sand Elemental Armor, a sand barrier that serves as his first line of defense. He even uses one as a form of a transportation/protection hybrid in the Deidara fight.
 * Gajeel from Fairy Tail uses his iron-based abilities as a source of Nigh Invulnerability. He is quite literally Made of Iron.

Comic Books

 * Magneto from X-Men can create electromagnetic forcefields as a form of defense.

Video Games

 * When Mega Man uses Wood Man's powers in Mega Man 2, he would have a flurry of leaves used as a shield as long as he remained stationary.
 * World of Warcraft has a vast number of these, and most caster classes have at least one. Although many of them, while called "armor" or "shield" don't actually protect the user, but provide different buffs.
 * Champions Online has blocking powers made from such diverse things as ice, fire, electricity (somehow), darkness, psionic projections, magic, and even kinetic energy (however that works).
 * Sonic 3 and Knuckles uses three shields: Fire, Water, and Electric. The fire shield protects from fire-based attacks as well as lava, and allows you to dash forward. The water shield allows you to breathe underwater and has a bouncing double jump. The lightning shield allows you to magnetically attract loose rings (so no, the ones in the item boxes don't count), but not the ones you lose as a result of hitting a badnik, as well as a double jump.
 * The three of them reappeared in Sonic Generations, but only if you unlock them in the challenges.