Don't forget the epic Magikarp Sweep. The reason it can 1KO is because its part of a Baton Pass team, set at 1 HP behind a Substitute, it does up to 200+, with Focus Energy, Swords Dance, and plain tricking the opponent. Its faster then just about anything, if you train it right, and can take down an Uber Team. Magikarp's level is usually 100. As for competitive use.
Unless you battle SF. Then it might get challenging.