Dinobot is one of the Maximals in Beast Wars. In the very first episode, he appears as a Predacon, but abandons his former comrades after he believes that Megatron has led them poorly. Note that this Dinobot has very little in common with the Dinobots of Transformers fame.
Dinobot is one of the most powerful and dangerous fighters in the series, especially the first season, before most of the other characters get a power upgrade known as going Transmetal. He is a proud warrior, always willing to fight for a good reason, or no reason at all, even. Some of the funniest lines in the series also come from him. (Many comparisons can be made to Vegeta of Dragonball Z).
Rattrap claims not to trust him, as a former Pred, but in time we see that they truly are close friends.
He dies saving the world single-handedly from the Predacons. I cried when I first saw this episode; he was one of my favorite characters, and his death very sad and heroic. The setup for this event was that Megatron had gotten ahold of some alien technology which allowed him to know exactly what to do in order to prevent the Autobots from ever beating his predecessor, also named Megatron (as seen in the classic 80s Transformers cartoon). I should note that this was possible because Beast Wars takes place several tens of thousands of years before the Autobots arrived on Earth. Megatron was basically slaughtering the early humans, in an effort to eradicate them so the human race would be unable to help the Autobots in the 80s. Interestingly enough, he got the technology because Dinobot gave it to him (it's a long story).
Megatron resurrects him, sort of, in the form of Transmetal Dinobot. However, while this Dinobot looks vaugly like the old, he has little of the old personality (though the new Dinobot also ends up betraying Megatron).