The Glock is a family of semi-automatic and machine pistols that uses a modified Browning locked breech short recoil operating principle. It is used prominently in Terminator: The Sarah Connor Chronicles by both Sarah Connor and Cameron Phillips.
In May 1980, the Glock company was invited to bid on a contract to supply the Austrian military with a new duty pistol to replace the World War II-era Walther P38 service pistol. Samples were submitted for assessment trials and, after passing all of the exhaustive endurance and abuse tests, Glock emerged as the winner with the Glock 17 model. The handgun was adopted into service with the Austrian military and police forces in 1982 as the P80 (Pistole 80).
The Glock 17 features heavily in promotional material and is used often by several characters in the show, Cameron and Sarah especially. The Glock's most notable appearance was in "Samson & Delilah" where it was used by Sarkissian's thug during the house raid. This same weapon was then used by Cameron after having killed the thug and it was very nearly the gun that took John Connor's life after Cameron reverted to her Skynet settings. It was later recovered by Derek Reese during his search of the burnt-out house whilst disguised as a fireman. John uses this gun to keep Sarah and Derek from interfering with Cameron's reactivation and gives it to her as a sign of trust, after which she gives it back and he subsequently throws it back to Sarah.
A Glock was also used by Cromartie during his first attack on John in the Terminator: The Sarah Connor Chronicles pilot episode and was likewise the last pistol he'd ever wield in "Mr. Ferguson is Ill Today" before being terminated. The Glock 17 has also appeared in the hands of various other characters throughout the series, though it's prevalence is offset by the Beretta and Colt models used interchangeably by the main characters. A silenced variant was also used by Derek to assassinate Andy Goode.