A graviton surge is a highly-energetic phenomenon which can be utilized to propel a vessel into null space.
Such a technique was used by an alien named Tash, who constructed a catapult in an attempt to return to his homeworld, from which he had been stranded while exploring an unstable wormhole. The catapult operated by locking onto a vessel with a graviton surge, and propelling it through null space, where it could theoretically emerge thousands of light years away. After Tash successfully used the catapult to travel five thousand light years, the crew of the USS Voyager utilized it to eliminate three years off of their journey back to the Alpha Quadrant. (VOY: "The Voyager Conspiracy")