[SixOfSpades]

If you could build Lurkers and tell them NOT to attack until you gave the word, that would be VERY effective against a Tank creep. Just let them creep until they're almost on top of you.....and SPIKE! Ouch. As it is, I dunno.....24 Burrowed Zerglings, and while they're busy making Zerg-burgers, send in a couple Scourges for the Science Vessel and Mutalisks for the Tanks? If you're Protoss, take 4 or more Templar as a group and spread them out a bit. Tell them to Psionic simultaneously--the Storms will spread to cover more area, ensuring you hit more Tanks. The Tanks should all fire at the first Templar, killing him and enabling the others to get their shots off. Or rush with a couple decoy Zealots first. For Terrans, I'd suggest Spider Mines, except that Vultures suck. So do Firebats.

I'd get my ass handed to me online....I've spent waaay too much time analyzing the AI. My strategy each game is not to expand, but rather to build up and reinforce my position until I can build 12 Battlecruisers, Guardians, or Carriers, plus whatever air support they need. Then pretty much nothing can stop me, except a lucky Plague or Psionic Storm.