I've been using Moleskine journals for years now. It's where I do most of my sermon work and and flesh out ideas and projects. I've tried other journals, some of which are spectacular (see Baron Fig's Confidant.), but I always come back to the Moleskine, large, softcover, dot grid.
But I also use a pocket journal, kept in my back pocket. In the past I used Moleskine's Cahier, but I've come to prefer the famous Field Notes brand pocket notebooks. It doesn't really matter what you use, it's how you use it that really counts.
Why Another Notebook?
I am a pencil and paper guy. It feels better and I am more productive when working with it. So a pocket journal is a good fit. I use it for keeping short lists, early drafts of article ideas, prayer requests, notes during meetings, and general brainstorming. I review the pocket journal often and transfer and expand important things to my large journal.
If you like pocket journals, or want to dive in, check out the Field Notes Pitch Black edition. It's a favorite of mine.