Originally Posted by
Gandariel
High Templars are AMAZING. Plus they can morph into Archons, which are not exactly the best unit ever, but help with mutas, do decent splash damage and make the HT useful in the battle even after having spent his mana.
The only things that resist both HTs and Archons are stuff like Ultras, Thors, Carrier and Tempest. (and roaches, to a degree).
The "by the book" counter of the HT is supposedly the Ghost, but for some reason Terran players seldom use them. (a shame actually, the EMP thing is cool vs protoss, and nukes are more viable than you'd think).
To sum up, HTs are awesome. And DTs are great too, and air is very viable as well.