Hok'tar is Goa'uld slang for advanced human. Such an advanced human would have a variety of abilities such as telekinesis and telepathy. The main Goa'uld involved in experimenting to create a Hok'tar is Nirrti.
Nirrti attempted to create a Hok'tar in order to have a host with preternatural abilities and tried to create one on two separate occasions. Once she tried to manipulate the people of Hanka in order to create a Hok'tar. This experiment was semi-successful as it gave Cassandra Fraiser the ability to manipulate magnetic fields, but it had a lethal side-effect, resulting in Cassandra being left gravely ill and near death. SG-1 was able to capture Nirrti when she invaded the SGC and forced her to cure Cassandra in exchange for her freedom. (SG1: "Rite of Passage")
P3X-367 was a planet where Nirrti took advantage of a people suffering from a plague to attempt to create a Hok'tar. Because the people of P3X-367 were suffering from a sickness, she offered to cure them, but instead of a cure, she manipulated their DNA with an Ancient DNA resequencer she found there in order to create a Hok'tar. When each experiment failed, she made their cells decay after a short period of time without constant maintenance. However, after learning the truth from SG-1, the people rose up against Nirrti and one killed her by breaking her neck via Telekinesis before using the DNA resequencer to make everyone's DNA right again. (SG1: "Metamorphosis")