Science Vessels are valuable additions to any Terran base or strike force. For 100 minerals, 225 vespene gas, you get a flying vehicle with 200 health. DEFENSIVE MATRIX
This is an innate ability to science vessels and cost 100 energy to perform. Use it to give an additional 250 hit points to target unit for about 30 seconds. Almost all damage is given to the matrix. Use it wisely on ghosts for nuking. Siege tanks are also great to matrix on.
The great unit, the battlecruiser is best to cast defensive matrix on, imagine a behemoth 750 hp flier that can wreak havoc!

IRRADIATE
Target creature becomes radioactive and creatures beside it takes damage. The spell lasts for about 30 seconds. Zealots, templar, scvs, barracks units and all zerg units are affected.
Use this to damage tight packs of units at once. Multiple irradiates do no harm but overlapping them will certainly kill a bunch of units. Hydras, marines and armies of zealots will be heavily damaged.

EMP SHOCKWAVE
The protoss killer, emp nullifies all shield and energy from its target. It affects many units in a 3 by 3 area. Use it always on archons and dark archons ! Battlecruisers with Yamato guns are also targets and especially all protoss units.