I'd agree with you about Cusack. Pesci is almost like a special case. The only movie you could really say that he ever "starred" in, meaning that it was really "his" movie, was "My Cousin Vinnie".

To me Frank Vincent and Steve Buscemi are perfect examples.

Vincent always plays the same character, always in a small role, and Buscemi is no star, but he's always playing those eccentric, unusual, quirky kinds of guys.