If u have scouted and see that your enemy has a weak air defense, build LOTS of scouts. (I use between 50-100!) Now, make one of your scouts patrol and make the rest follow by right mouse clicking on it. Then send your one scout to the enemy's base, the rest will follow. When the patrolling scout dies, the rest will go crazy attacking! Easy win! (Note: this also works with zerg mutalisks and terran wraiths).

CreepColony's Opinion: Umm...it is impossible to build 100 scouts...scouts are 3 psi each, 3 x 100 = 300, and 200 is the psi limit. Anyways, scouts are not that strong against ground, so I wouldn't recommend this strategy if they are going mass ground, or have a lot of air defense.