When I was a teenager, the actors I was really into were Mickey Rourke and Sean Penn. I saw 'Rumble Fish' on my 16th birthday, and around the same time, it was 'Falcon and the Snowman' and 'Bad Boys'...
It's always more interesting to take on someone that's going to have hidden sides or a fatal flaw, because there's going to be more to play with - more conflict, internally or in and around them - but...