* Ironhide: Killed by Shockwave while defending Sam Witwicky in Chicago.
* Jazz: Briefly seen as a ghost in the film, but his death is confirmed off-screen. It's implied he died during the Battle of Los Angeles in the previous film, Transformers: Revenge of the Fallen.
* Arcee: While not explicitly confirmed dead in the film, it is heavily implied that Arcee is killed by the Decepticons when she and Optimus Prime are separated during the Battle of Chicago.
It's important to note that while Arcee's fate is left somewhat ambiguous, her absence in subsequent films and the nature of her "disappearance" in Dark of the Moon strongly suggest her demise.
Some sources also mention the death of Dino in this film, though he doesn't appear in the movie itself. His death is mentioned in passing, suggesting it occurred off-screen.