What a necro thread. Anyway, for me:
Epitaph - the vocals are some of his most haunting/transcendent prior to stuff on Dreaming Neon Black. The music is decent too, but the vocals completely carry this song.
Communion, Seasons of Destruction and Battle Angels are my other favorites.
Honestly, I never really understood the whole "ahead of their time" praise that this band would get. Musically they were solid, but no one would have given them the time of day without Warrel. He's the entire reason the band had any attention. Otherwise, they would have simply been lost in the crowd with other "pretty good, but not spectacular" metal bands. I'm not saying that they didn't write good songs, because they did. But many bands write good songs.