CT

Also, current transformer. A device used in substations to alter the current before it is distributed to consumers.

Also used as shorthand for Counter-Terrorist in the mod Counter-Strike for Half-Life. Whereas "T" is short for Terrorist.

CT also stands for "Computerized Tomography," another term for a CAT Scan. CT scans aren't used as much now that we've got MRI, but patients who can't undergo MRIs (due to claustrophobia, metal in their bodies, and the like) often undergo CTs.