A hypo gun is a medical device used to do an easy inoculation of a serum or a virus, using a gun- based device with an attached syringe.
In Resident Evil
Resident Evil: The Umbrella Chronicles
Before his encounter with Chris or Jill, Albert Wesker inoculates himself with the prototype virus, given to him by William Birkin, before the Tyrant attack in the mansion laboratory. This gives him super-human strength and speed. This is only shown in Resident Evil: The Umbrella Chronicles.
Resident Evil: Degeneration
Resident Evil 2 / The Darkside Chronicles
Resident Evil: Operation Raccoon City
According to Inserted Evil, the U.S.S. member known as BERTHA uses a hypo gun in her special abilities. Also, U.S.S. field scientist Four-eyes uses a hypo gun to control the infected creatures, or cause infection to Spec. Ops/turn zombies into V-Acts.
Resident Evil: Dead Aim
Morpheus Duval injects himself the tG-virus in order to heal his fatal wounds caused by Fong Li.
Resident Evil Revelations
Resident Evil 4
Resident Evil 5
This item will be present in most the games, however it will be first available to the players in Operation Raccoon City as it's BERTHA's most used item in game.