(note: This works great on newbies and intermidate players but not expert, plus it needs a big map. This is used on people who like to turtle.)

Start out by getting atleast 9 drones getting minerals, forget gas at the moment. When you start getting money, build spawning pool and evo chamber. Start circling your base with spore/sunken colonys, while disriputing overlords around your base. Begin getting gas now. Start building nothing but hydras till you get to 150 population. Make the rest mutas. send mutas to attack they're base 4 at a time (THEY WILL GET WACKED don't sweat it). Keep it up building more mutas as needed. As you are sending mutas on they're suicide missions upgrade at the evo chamber and hydra's den all the way. Eventually they're gonna get mad/paniced and send all they've got at you, the combo of spore/sunken colonys(you should have 5 rings around your base),about 100 hydras and possably some stragler mutas will mow them down flat. You should have atleast half your hydras left, quickly fly some mutas to just out side they're d's range and morph them to guardians with your hydras there for back up. When the metamorphasis is complete send them in, they should have little resistence. the guardians taking out they're d and the hydra's everthing else, because they just lost they're army at your base. This works best on toss, with some draw backs againts terran (comsat takes away the element of surprise) and Zerg (they can rebuild at your speed so you have to be faster).
Again this is for turtling newbies, not to be used on experts. I have done this successfuly on reasonably good players, tho it's a challange.

CreepColony's Opinion: Cool, but some sunkens and spores inside your base would help.