Lie has a kick-ass riff.
I love Peruvian Skies' riff from 4:19.
The chorus riff of Misunderstood fits the song magnificently.
TGP is full of beautiful riffs. Any of the 12SS (except Repentance, I don't really like it) has beautiful riffs.
ToT is a really heavy album, contains some of the best riffs ever such as the intro of As I Am or right Honor Thy Father right after the 33rd second.
TRAOE's intro is great, but TSF has an even heavier feeling to it right before that solo.
Sacrificed Sons also sounds very good at the chorus parts.
8VM has so many, I can't even comprehend many
SC is also full of great riffs, like ToT. I especially like Forsaken, TDEN, TMOLS and ITPOE.
BC&SL has that amazing two songs, TCOT and TSF are amazing in means of EVERYTHING.
Well, thinking about it again, any song in that album has magnificent riffs.
ADTOE? BMU, BMD somehow lacks power but has very good sounding things. Lost Not Forgotten, Outcry and BAI have tasty riffs.
DT12 has the "chocolate cake" tone, so whatever JP plays with it sounds great! But TEI and anything from IT sound way better than the rest.