Fun trivia, the on-box description of Destroyer is "Enemy Robot Attack Tank". Meanwhile the on-card description of Tank is "Enemy Robot Destroyer"!
Defender was my favorite. He had some decent articulation and was about as close to a traditional Transformer in design as they came.
Loco and Super Leader One. I really like Scooter and Cykill too. We counting Rock Lords, cos Boulder is awesome too.
Tank came out in the very first wave first in late 1983, Destroyer was 1984. I really like Super Warpath as a toy. The black helicopter. He was an apache Helicopter with a rotor on his chest!
My fav on the cartoon was Turbo, but I never had the toy. I only had Leader-1, Jeeper Creeper, Scratch, and the Command Center. The coolest Gobots are Tux (because top hat) and Bad Boy (because he's an A-10... a cooler A-10 than Powerglide).
I never played with/had any of the the figures or saw the cartoon but what little I do know I have to say Leader One & Cy-Kill are my favorites.
Just for nostalgia sake I'm going to say my faves were Fitor and Jeeper-Creeper because those were the only ones I had them as a kid. Even though technically Jeeper-Creeper belonged to my brother.