Let's face it. I am triple-extra large. At 6 feet, 8 inches and 300 pounds, I have special size needs when it comes to most things others take for granted, such as clothes, furniture, and, believe it or not, keyboards. My favorite keyboard, beating out even the old Northgate keyboard, is the IBM AT/PS2 Buckling Spring. This used to be sold by IBM as the "Enhanced" keyboard. This type of technology gives an audible click when the key is struck and when it releases. So, the keyboards are noisy. However, this can be turned to one's advantage, especially at work, because you can be heard being productive. The springy feel of the keyboard is just right for people like me, who began their typing life on electric typewriters. The keys are also larger and spaced more appropriately for my hands than smaller keyboards, particularly those on laptops.
Unfortunately, IBM/Lenovo no longer manufactures these keyboards. But demand is high enough that a company named Unicomp bought the technology and has continued to manufacture the keyboards. At home I still use my IBM Enhanced keyboard for writing, though I use my Microsoft cordless for surfing.
I also like to write long-hand from time to time. This rarely amounts to more than jotting down ideas, but sometimes I'll sketch out rough scenes. When I'm writing long hand it is almost exclusively description or scene setting, the more poetic part of fiction writing. When I'm writing action or dialogue nothing works better than the keyboard.
For long hand writing I prefer the Waterman Phileas rollerball pen with a Pilot G2 Gel insert. (The Pilot inserts fit nicely into the Waterman Phileas, and they're one-third the price). G2 Gel ink is quite simply the best ink on the market for writing. Smooth, black and doesn't bleed.
Having the proper instrument enhances productivity if not creativity. While I have very specific opinions about Pens and Keyboards, my attitudes toward paper are not as well defined. I like to use the brightest white I can find, with the best cotton mix, with no watermark. My favorite right now is the Hewlett Packard Ultra White Ink Jet paper. I use inkjet paper in my laser printer as well, because it is slightly stiffer than xero-copy paper, and doesn't curl as much.