Heroes of Newerth 15 Minute Challenge
I invented my own game using the Heroes of Newerth (DotA) gameplay. The game is called the HoN 15 minute challenge. The challenge consists of playing a practice game of HoN, and completely destroying the enemy as quickly as possible, ideally within 15 minutes. It's a challenge of your ability to attack quickly and effectively, and to take towers out.
This challenge is also interesting because it represents the fastest possible time you could defeat an enemy in a 1v1 game.