I have the RCA CD with the Leone trilogy, as well as, "Once Upon A Time In the West" and "Giu La Testa."

Thanks for your suggestions in advance.

Plindboe where are you man, Peter has over 300 Morricone scores so He's the man to ask?!

A lot of the important ones have been mentioned (My Name is Nobody, Il Mercenario, La Resi Dei Conti), but I would add scores like Tepepa, Vamos A Matar Companeros, Ringo etc to the list.

Bond, nearly all Morricone's westerns are good, each in their own way. I think the only one I don't care much about is "I crudeli"(The hellbenders) since it's kinda monothematic. It's a great theme, but usually Morricone's westerns have several great themes to enjoy.

These are in my opinion the must-haves:

1966-Navajo Joe
1967-Faccia a faccia (Face to face)
1967-La resa dei conti (The big gundown)
1968-E per tetto un cielo di stelle (A skyfull of stars for a roof)
1968-Guns for San Sebastian
1968-Il grande Silenzio (The great Silence)
1968-Il mercenario (A professional gun)
1969-Un esercito di 5 uomini (The five man army)
1970-Gli avvoltoi hanno fame (Two mules for Sister Sara)
1973-Il mio nome e' Nessuno (My name is Nobody)
1975-Un genio, due compari, un pollo (The genius)
1981-Occhio alla penna (A fist goes west)

The two last ones, are more cute and silly, than actual western sounding(especially "Occhio alla penna"). They are still wonderful though, crammed with themes. Tell me if you need details about any specific score.