I'm gonna have to read through all this thread because I just started listening to these guys a bit after they popped on my Pandora.
I keep hearing potential but have yet to hear the one song that really grabs me.
Here are a few of my favorites just scattered from their various albums:
From their first album (Symmetric in Design):
(this is one of my all-time favorite songs by them and actually one of my all-time favorite songs by anyone)
From their second album (Pitch Black Progress):
(I think this is a decent song, but not one of their best, but it is their most famous song and their first music video. I definitely recommend watching it)
(Another one of my favorite Scar Symmetry songs. I love all the vocals on this one.)
From their third album (Holographic Universe):
(Their second music video. Not one of the best songs on the album, but maybe one of the catchiest)
(Another one of my all-time favorite songs, not just by Scar Symmetry but period)
After the third album, their first singer (Christian Alvestam) left the band and they brought in two singers to cover the vocals: one clean singer and one growler/screamer. Ironically, even though they split Christian's job into two separate people, neither of the singers were anywhere as good as Christian. This is something that almost every single review of their fourth album (and many later albums as well) mentioned, how the new singers couldn't match Christian's vocal skillz.
From their fourth album (Dark Matter Dimensions):
(This is overall a decent album, but nowhere as good as the first three)
I would post something from their fifth album, The Unseen Empire, but it's the only album of theirs I don't own.
From their sixth album (The Singularity Phase 1: Neohumanity):
(I already posted a song from this album up above, but this is the song that several people have mentioned as awesome. This album is the first album with the new singers that I think is actually REALLY REALLY good)