Shockwave staged a comeback in 2005's Transformers: Alternators toy line, which featured classic characters re-interpreted with modern vehicular alternate modes. Although the American toys offered no supporting fiction, the storyline included with the Japanese version of the line, Binaltech, detailed the story of Shockwave's rebirth in this unusual new form.
When the time-displaced Decepticon agent, Ravage, used the time machine called the Kronosphere to alter the time line (branching off the Binaltech/Alternators storyline from the continuity of the G1 animated series), the chaos that ensued resulted in the destruction of Shockwave's body. With Ravage's aid, his mind was installed into a stolen Autobot "Binaltech" body, equipped with a prototype "Transmuter" device, which, when interfaced with Shockwave's personality component, allowed the chassis to "transmute" itself into Shockwave's recognizable physical form, including his cyclopean visage and gun-arm. He wields a Turbo Rifle which can also serve as a power booster for his gun-arm, and can project up to five holographic duplicates of himself anywhere on the planet (an ability mentioned in the series bible for the original animated series, but never put to use until episode 4).
Read more about this topic: Shockwave (Transformers), Transformers: Generation 1