I always liked Grimlock. I used to do his voice and speak patterns when I was little. “Me Grimlock kick butt.” “Me Grimlock not dumb, me king.”
During the third season of Transformers, there was an episode where Grimlock became intelligent, he actually became one of the most intelligent Autobots on the team. He even creates a new team of Autobots called the Technobots.
I liked this episode, despite the poor animation. I thought it was honorable thing to do when Smart Grimlock gives his intelligence to the Technobots, and Grimlock reverts back to his stupid self. (However, it would have been far more compelling if Grimlock stayed intelligent throughout the rest of the season. I think they dropped the ball on that one.)
You throw in an appearance by Unicron, and you have a pretty good third season episode, minus all the bad animation flaws. (Rodimus Prime transforms into Hot Rod’s car mode in this episode!)
Note: When did Cybertron get giant organic fish in their lakes? Because the Dinobots claim they go fishing all the time with Grimlock.