I'll limit my list to one film per director as well. ABC order:

Agguire, Wrath of God (1972; Werner Herzog)
Blue Velvet (1986; David Lynch)
The Deer Hunter (1978; Michael Cimino)
The French Connection (1972; William Friedkin)
The Godfather part 2 (1976; Francis Ford Coppola)
Mean Streets (1973; Martin Scorsese)
Once Upon a Time in America (1984; Sergio Leone)
Southpark: Bigger, Longer and Uncut (1999, Trey Parker)
Unforgiven (1992; Clint Eastwood)
Vertigo (1958; Alfred Hitchcock)