Mine would probably be the solo in Serenty-Painted Death. I love it so much and especially how it goes into that singing part right after it. Pure perfection.
It's really hard to say, because there are so many that I like, but the main ones that come to mind are either the one from The Leper Affinity, or maybe the one from the Drapery Falls the way its played on Lamentations (and probably on many other live occasions.) I also really like the solos from A Fair Judgement, Windowpane, and the one at the end of Hours of Wealth.
I agree with a lot of the solos are listed, deliverence and a fair judgement are great, the lighter solos are usually my favorites. But my true fav, even though its short, is probably masters apprentices... main reasoning being it was probably the first i actually to the time to learn to play.
serenity painted death, windowpane, ghost of perdition, beneath the mire, hours of wealth, benighted, white cluster, when, to bid you farewell, forest of october, funeral portrait, leper affinity, deliverance, a fair judgement...
So many, but these are the ones I can think of while blasting April Ethereal.
The slow one in Windowpane.
I really love Steven Wilson's solo in Bleak.
A Fair Judgement - All
Hours of Wealth
Epilogue
Ending Credits - I could listen to this for hours.
All the lead work in Godhead's Lament.
The last 10 notes of the Serenity Painted Death solo make it something special. Also, the solos on the GR are fantastic throughout.