Cell phone

The Cell phone likes to ring. A lot. Which isn't wise around mischievous, homicidal robots.

Fiction

Revenge of the Fallen novel

Much like most other appliances in the kitchen, the cell phone was brought to life when Sam's Allspark shard fell into the kitchen. Its first act of life was to ring incessantly, which prompted the nearby microwave robot to put him in his chest and fry him. Revenge of the Fallen (novel)

Trivia

• In the movie itself, a cell phone is right next to the microwave. Hmmm...
• Likewise, the Microwave bot's concept art shows a cell phone in his chest...