Resource Guarding - Scout out ALL resource areas using cloaked units (burrowed Zergling, Protoss Observer, Dark Templar, Terran Spider Mine). Then whenever your opponent starts to build an auxiliary base at any resource area, send in some guys to kill him. Repeat until opponent's resources are exhausted, leaving him unable to make reinforcements to support his main base defenders.
Invisible Wall - Make a group of Dark Templars (about 3-4) stand in a row at the top part of a ramp leading to your base.
Eat Green Shit (Terran vs Zerg) - Make lotsa Science Vessels. Abuse Irradiate. Uber Micro recommended
Your Dudes Are Mine, Sucker (Protoss vs Anyone)- Same as Eat Green Shit, except replace Science Vessels with Dark Archons, and Irradiate with Mind Control
False Transport Convoy - Make a group of shuttles/arbiters. Have lots o' High Templars use Hallucination on them, and have the Hallucinations surround the real shuttles/arbiters. The Hallucinations should take the brunt of the damage, leaving the real ones relatively free to drop/call in a decent-sized Archon/Reaver/Dark Templar/Whatever raiding force.
Double Nuke - For when one Nuke just isn't enough to take out that damn heavily fortified building cluster.
CANNON RUSH KEKEKE - Focus a lot on gathering minerals, while sneaking a probe into your enemy's base to build pylons/photon cannons. At least if this fails, you should still have a lot of minerals to make Zealots, Photon Cannons, and Scarabs/Interceptors
Instant Win - Mass Carriers. When Victory Screen appears, be sure to click "OK."