I build Hecarim as a tank and really enjoy him for that roll. He's more of a damage dealer than a protector, but if you enjoy initiating team fights, running down carries, and chasing down anyone who tries to gimp away at the end of it, Hecarim is your guy.
That said, many people think that Hec is UP. I personally don't, maybe a QoL buff is all I could see giving him.
Other good tanks to look into are Naut, and Maok. Both of these have amazing ganks. Their late games aren't as good as Hec's, but their early ganks can be devastating.