StarCraft: Brood War/Protoss Mission 3: Legacy of the Xel'Naga

The mission starts with a scripted sequence as a set of Corsairs disrupts the Zerg colonies in the top-left corner, clearing the way for shuttles to deliver a team of dragoons. Use the dragoons to kill the hydralisks, then the sunken colonies. The disruption webs will end before you're done, so get your corsairs out of range of the spore colonies. Once this is clear, make plans to expand here eventually.

Now you need to make your base secure. The enemy will make regular Overlord drops on your base, all along the coast, first in single drops, then in waves with Mutalisk air support. Station your corsairs and dragoons here at first to discourage this. Remember to order your Corsairs to "Hold Position", or they'll chase off the first unit they see, right over the Zerg base! Start building pylons and photon cannons along the coast near your base to secure it. Include a few guarding the bridge in case the Zerg land in the top-left. This will be expensive, but much cheaper than rebuilding your base.

Now it's time to build your army. You'll need Reavers to lead the charge, Shuttles to make your landing, Corsairs to clear the landing zone and provide air cover, and Dark Templars to make the kill. Gather resources generously, since you can build another base to the northwest. Focus on minerals, since Reavers are expensive and so is their ammo.

Save your game before you attack, just in case it turns out you need a bigger army. Now you're going to repeat the stunt from the opening. Use corsairs to disrupt the Spore colonies, and rush your shuttles in to drop. The battle will become absolute bedlam as all the burrowed Zerg come out of the woodwork, but don't get bogged down. Keep moving your Reavers forward towards the Cerebrates. Your main goal is to clear out Sunken colonies, as those will tear up your Dark Templar in a hurry, and their cloak won't help with so many overlords around. Keep your Reavers attacking structures, and order your Templar to stay close to them to kill Zerglings and Hydralisks. If your Templar wander off to attack random buildings, they'll be killed easily. Once the Sunkens are swept away, rush your templar in to kill the cerebrates. Watch the ending sequence and you're done.