What I do is with every prestige, try out and get mastery on weapons I haven't gotten around to using yet. Just pick two or three and go for it. The XP is nice, and it's a nice challenge.
I like working on my k:d ratio. CoD: World at War was perfect for run and gun but you really get punished for that in MW2. You can always throw on an acog or quick scope people, and run with your snipe!
I like the FAL with ACOG, but I only use it occasionally on big maps. Iron sights are good if I'm going working FMJ for full mastery and want to keep marathon. Otherwise I use bling and keep a holographic on most of the time.
You're probably thinking that because of the checkboard weave. As far as I've read on here, some prostocks just come with a different weave. Same stick.