For those of you who know me or work with me, you'll eventually hear that I'm trying to be "paperless." I don't like big stacks of paper on my desk. I don't carry around a notebook. I hate those big PowerPoint presentation that equate to half of the rain forrest in paper.
My main productivity application is Evernote. I use it on my various Macs or PCs; iPhone and iPads (1 and 2). In fact, it's probably the one productivity application I can't live without. There's a reason why the logo is an Elephant. It helps me remember everything.