Interesting style

  (Edited: )

Splash damage units only?
As zerg, you can only get banelings (lings may not attack), mutalisks, ultralisks, infestors (fungal only). Meaning no queens, no hydras, no corruptors, no broodlords, etc.
As terran, you can only get hellbats, hellions, ravens (seeker missiles only), siege mode tanks (not unsieged), ghosts (only for nukes).
As for protoss, a bit difficult to impossible, Archons, Colossus, High templars (storms only). 
Or reverse, no splash damage units.