Advent (3:19 to 4:21)

Sad to say that's the standout moment for Opeth's bass. I'm might be wrong, but it's the only place I can remember it doing something that's different than the guitars and at the same time being extraordinary. Advent is so damn melodic.
 
^ The outro to Nectar and the Intro to To Bid You Farewell...heck many places on Morningrise.

and parts of Bleak and The Drapery falls.
 
Dante's Inferno said:
Sad to say that's the standout moment for Opeth's bass. I'm might be wrong, but it's the only place I can remember it doing something that's different than the guitars and at the same time being extraordinary. Advent is so damn melodic.

To Bid You Farewell's double tracked bass in the middle (around 5:15 in I think)
The Drapery Falls's intro riff
Most of Damnation
Blackwater Park's slap bit
There's a few solo bass parts scattered over Orchid and Morningrise, such as 7:30 in Black Rose Immortal
Face of Melinda

Just a few for you.