Waylon Smithers

Waylon Smithers is the assistant of Mr. Burns and althought normally not that bad a person he is obscenely loyal to Mr Burns (to the point it is heavily implied he is gay) - although it is worth noting that Smithers is often the subject of abuse rather than malice on his own part: he is shown to have a jealous streak and can be rude and even (on occassions) physically violent towards those he dislikes and can be sneaky, in general though Waylon Smithers is a minor villain and toadie rather than a fully-fledged evil-doer.

Trivia

 * Smithers was voiced by Harry Shearer in The Simpsons.
 * Waylon Smithers is very rarely called by his full name in the series, he is usally refered to simply as "Smithers"
 * a running-joke in the series is Smither's blatant homosexuality (which Mr Burns seems oblivious to)