For Whom the Bell Tolls, but honestly I like hearing it live way more than the original album version.
I think Death Magnetic is pretty awesome. After the absolute crap that is St. Anger I wasn't expecting much but DM really blew me away. The only 2 songs I don't care for that much are Judas Kiss and Unforgiven III. The rest are great, and they just released a 4 song EP of songs that didn't make DM, and I like all of them.
Justice is probably my favorite album of theirs, but to be honest as crappy as Load through St. Anger is, there are still some songs on those albums I like. Even St. Anger I think The Unnamed Feeling is a good song.