Click on the images below for more details on each controller. Some of the older controllers can still be found in the likes of Japanese auction sites. See this OneSwitch Blog post for more.
Many of the controllers below can be made to work with most games machines or computers with suitable controller adapters.
Please feel free to e-mail for help on anything that is unclear.
Game Control Mixer 1 Handed adapter. Convert standard controllers to one handed.
A well built controller from HORI. D-pad is for left-handed use.
Ambidextrous One Hand gaming controller.
3 modes of play: Conjoined, two halves or one handed (right-hand).
Finger controlled Dance mat.
Stick has three switchable modes: D-pad, left-stick and right-stick.
Basic PSone era gamepad. Some controls can be remapped.
From Evil Controllers
Various well priced one handed solutions for PS4 or Xbox One.
From Ben Heck
A heavily modified Xbox One controller for left or right-handed use.
A Playstation 2 digital controller with 14 buttons and 2 digital thumb-sticks.
Discontinued rare controller with interchangeable control pods.
Many Nintendo Wii games can be played one-handeded. This NeoGAF post lists some of them.
One hand controller designed to be used with the PS3-SAP module.
One Hand Gaming News - Via the OneSwitch.org.uk Blog.
Controller Adapters - Enabling Playstation controllers to be used on alternative games consoles and computers.
SpecialEffect post on using a Xbox Adaptive Controller for one-handed play.
Archive: Accessible GameBase One Handed forums - Direct link to a one-handed gamers forum. See also the Game-Accessibility.com forum.
One Handed Games List - for multiple game platforms.