Here’s an interesting post on Lifehacker: What’s Your Fastest Text Input Tool?.
I’ve been using full-sized keyboards for a *very* long time now so that blows everything else out of the water for me. When I’m motivated I can type at speeds exceeding 100 words per minute, although that’s typically not necessary with the stuff I do.
I’d rank pen and paper as second. It’s pretty much a necessity in university when you’re taking down notes and whatnot. Although some people can get away with using laptops in class, I find that it’s extremely hard to copy out diagrams and mathematical equations. Perhaps this is some indication that I should learn LaTeX or something? 
Next up would probably be a close race between my Wacom tablet (using Window’s handwriting recognition software) and my iPod Touch. I’m still rather slow at both, although that might just be because of a lack of practice.
In last place is a standard phone with a three-letters-per-number keypad. Yeah. I don’t use my phone very often and I text even less.