Parts? Like lead, rythm, etc.? I love to play both actually. In my band I actually play solos and awesome riffs, but I'll also go back and play background.
You might also be talking about the actual parts on a guitar. Haha, I doubt it, but my, "favorite," would be the neck I guess. That's where you make the music!
Ahhh, I see. Well my favorite part to play the bridge of "The Crowing" by Coheed and Cambria. Here, I'll give a link so you can hear it. The part I'm talking about is at 2:53-3:30 [url]http://www.youtube.com/watch?v=scARFVFIluw[/url]
I love the intro/verse on Never Too Late by Three Days Grace. It has a really clean feel to it, and is a piece of brilliance if played on acoustic. It is so epic!