During the Future War, Skynet have developed various of Hunter-Killer Series against human. Those machines are categorized into different series according to their functions:
- A Series - Aerial Hunter Killer
- G Series - Ground Hunter Killer
- D Series - Defensive Installation
- I Series - Infiltrator or Initiate (Depending on timeline.)
- T Series - Terminator
- HK Series - Hunter-Killer
- A, G, and D series are only mentioned in the video game The Terminator: 2029 , while in most of the Terminator fiction, the A Series is simply referred as HK-Aerial.
- HK series is only featured in The Terminator Collectible Card Game
- I series only appeared in T2 Trilogy and The Terminator: Dawn of Fate.