10. 'The Wolf of Wall Street' (2013)
His part is nothing more than a glorified cameo — but, good lord, what a glorified cameo! Responsible for portraying the influential mentor who will set Leonardo DiCaprio's Jordan Belfort down the path of wickedness, McConaughey practically hums as Mark Hanna. (Actually, make that literally hums.) A sociopath with a killer smile and great suit, Hanna supplies Belfort with his ethically slippery North Star. Every terrible thing Belfort does for the rest of the film? It all goes back to McConaughey's crucial, coked-up guest appearance.