Fireball

The fireball is somewhat of a videogame staple, nearly as ubiquitous as dot bullets in a shooter. Over the years they've functioned as traps and objects to avoid for fear of instant death in platforming games. 
Powerups to grant fireball throwing powers to your own character are quite common in platformers, and are featured quite prominently in the Mario series. The fireball power is bestowed on Mario and Luigi by the fire flower, and Bowser himself is quite content to spit fireballs at the player in many of the games.

Fireballs also play a large role in RPGs, especially those based on Dungeons & Dragons. The fireball spell appears in almost every TSR-licensed game as well as those based on other fantasy universes from The Elder Scrolls to Warcraft and Diablo. It almost always functions as a slow projectile, exploding on contact and damaging nearby enemies - including your own hero if you were foolish enough to throw it at an object mere feet from your own unprotected face.

As traps, fireballs appear as both small, fast moving projectiles (usually launched from a source in a wall) and huge, fiery boulders that crush as well as burn. God of War featured a reasonably large portion where you had to dodge rows of incoming flaming boulders as Kratos. How rocks can be set alight is never explained, although as the source of fireballs is almost always mystical, explanations aren't particularly necessary.