5. 'Gangs of New York' (2002)
At the time of DiCaprio's first collaboration with Scorsese, many were initially perplexed: Pretty-boy heartthrob Leo making a period picture with the king of fast-talking criminals? But the actor wasn't a bad fit for the role of Amsterdam Vallon, an Irish-American young man biding his time in order to avenge the death of his father (Liam Neeson) at the hands of the Nativist gang leader Bill the Butcher (Daniel Day-Lewis, in what might be his greatest performance). More befuddled than rough, Amsterdam has to grow into the role of gang-leader himself — and Leo plays him as a brooding naïf, an ideal approach against Day-Lewis' boisterous, whip-smart villainy.