My top-ten western list is pretty much just Clint Eastwood and Sergio Leone - sorry!
1 - Sergio Leone's Once Upon A Time In The West
2 - Sergio Leone's The Good, The Bad & The Ugly
3 - Sergio Leone's For A Few Dollars More
4 - Clint Eastwood's The Outlaw Josey Wales
5 - George P.Cosmatos'/Kurt Russell's Tombstone
6 - Clint Eastwood's High Plains Drifter
7 - Clint Eastwood's Unforgiven
8 - Sergio Leone's A Fistful of Dollars
9 - Sergio Leone's Duck You Sucker/A Fistful of Dynamite
10 - Tonino Valerii's/Sergio Leone's My Name Is Nobody
Edit: Added Leone's name to My Name Is Nobody since he directed around 10 minutes of it.