StarCraft/Protoss strategies

Zergling Rush
Try to play against your opponent in a small one-on-one map that you know very well. Send your four drones to start mining minerals and order your overlord to your opponent's base. Hatch a drone and order this one to mine too. When you reach 200 minerals, order the drone to morph into a spawning pool. Once it's done, hatch 6 zerglings (two for each egg) and rush to your opponent. If you are lucky, you will catch your opponent with his pants down. Try to kill as many of his workers as possible and you will be guaranteed a win. If your zergling rush fails, you will fall behind in mining resources. Most experienced players know about this rush and can defend well against it so be careful of whom you use this strategy against.

Counters:
 * Terran - Build an early bunker near your resources and place one marine inside.
 * Protoss - Build two gateways and try to have two zealots come out by the time the zerglings arrive.
 * Zerg - Get an early sunken colony as well as a few zerglings to defend it near your resources.

Lurker Rush
Lurkers are fun to use against Terran and Protoss because of their lack of mobile detectors in early mid-games and therefore can be used to secure vital locations early on. First build a second hatchery, then a spawning pool, and an overlord. Remember to keep making drones to collect minerals. Then select a drone to morph an extractor over a vespene geyser. When it's done, select four drones from your minerals to mine gas. After you have 100 gas, upgrade your hatchery to a lair, then spawn an overlord, and build a hydralisk den. Once your lair is complete, research lurker aspect and spawn another overlord. Make four hydralisks and morph them into lurkers when you have finished researching. Now charge them into the enemy base, ignoring any hits, and once you reach his resources patch, burrow them. If this is successful, it's basically game over for your opponent. Yipee! You might also want to harass him with a few zerglings beforehand when you are trying to do a lurker rush.

Counters:
 * Terran - A marine-filled bunker with a nearby missile turret and a siege-moded siege tank placed near your resources or a choke point.
 * Protoss - About two photon cannons placed near your resources or a choke point.
 * Zerg - Overlord?

Mutalisk Rush
Mutalisks are fast flying zerg units and can be really annoying if used properly. They are good to use against Zerg and Protoss, and maybe against Terran too. They require a lot of gas though so build an early extractor followed by another hatchery and a spawning pool. Upgrade the hatchery to a lair. Don't forget to make more drones and overlords in the meantime. Build defenses if you have to, but not too much. After lair is done, make a spire. After the spire is done, make 6 mutalisks and rush them to the enemy base. If there are no anti-air defenses near the enemy's resources, then whoopee! Kill all his workers. You can also kill his army if his troops can't attack air.

Counters:
 * Terran - A marine-filled bunker near your resources. A large marine army with medic support is also nice. Upgrade U-238 shells and stimpacks. The stimpack upgrade is also highly useful here and can of course be used liberally thanks to the medics nearby.  A fair supply of missile turrets are probably the best defense going for Terrans though.
 * Protoss - Photon cannons near your resources. Maybe early corsairs.
 * Zerg - Lots of Hydralisks and spore colonies near your resources.