This article or section contains obsolete information, but exists here for historical purposes.
Surge was a 'non-targeted' Summoner spell available in all game modes. As part of the season three overhaul, this summoner spell was removed. Its functionality was added in-part to Guinsoo's Rageblade, which uses Surge's icon while in effect.
It was a highly efficient tool for all AP characters pushing turrets as, unlike towards any other targets, if 40% of your AP is greater than your AD bonus your champion is going to add that amount to the base damage of the autoattack instead of the bonus attack damage. The bonus attack speed helps significantly, as well.