You know how only biological units are affected by Science Vessel's Irradiate? You can take much advantage of this by irradiating your own unbiological units (for Terrans, basically anything that doesn't come from the Barracks or Command Center) and moving them towards biological units. You can use this VERY WELL on Zerg! Also, you can try irradiating a flying unit (say a wraith)and sending it straight for the collectors (excepting the Protoss). Actually, if you're playing against Protoss, this strategy is useless, because only the zealot and the High and Dark Templars are biological. The best thing about this strategy is that if you do it carefully, none of your units will suffer damage from the spell.

CreepColony's Opinion: Irradiate doesn't have a very large splash range, so you irradiating more than 1 unit would be helpful.