Malcolm McDowell has also had some more obscure
roles, some of which are only notable
because he played them.
He played a heretical cleric in the Lexx movie Gigashadow; there were Shakespeare quotes included in the script, which I suspect would not have worked in such a bizarre sci-fi setting if not for the casting.
Although I don't think he was credited for this, he also appeared on South Park as the guy reading a book in front of a fire for the most twisted version of Great Expectations I've ever heard of. His opening line was, "Hello. I'm a British person."
Just a few months ago, I saw A Clockwork Orange for the first time. The friend I saw it with said, "He's a character actor, and this movie defined the character." I didn't really believe him. My primary thought throughout the movie was "That's really Malcolm McDowell???" I had never seen him young, or so I thought. I later learned he was also in Time After Time, a 1979 movie in which he played H.G. Wells chasing Jack the Ripper into the future. But I didn't remember his face from that. When I watched Gigashadow again afterward, I saw the connection. Age and role aside, the face was exactly the same, including odd expressions I hadn't remembered seeing him do before. I guess my friend was right.