Japanese manufacturer Sanwa Denshi has created a special one-handed Playstation 2 controller, designed to work with the online-only Final Fantasy XI. Apparently the control in FFXI are so basic that you only need a D-pad and four buttons, though, and not the full compliment of shoulder buttons and the like - making it wholly unsuited for most other games. That's too bad, too, because all jerk off gamer jokes aside, one handed controllers are a fine idea for RPGs and other games that don't require precise, frantic input. There was a einhanded controller for the original Playstation, if I recall. Somebody should re-release that for the PS2.
Oh, and I like the retractable cord!
Read - Final Fantasy XI Gets its Own Special One-Handed Controller [Spong]