I'd agree with DarkHyren and go with an MP Wheeljack. He's important in the cartoon and pretty consistently important throughout G1 continuties.

My other suggestions would be Arcee or Omega Supreme. I think there's some third party MP like versions of both but am no expert. Arcee as "the female one" is very iconic, and if you ask people about stand out TFs from the cartoon I feel like Omega Supreme will always come up (more so than the other big guy Metroplex).