Click-to-Move / Mouse-to-Move
Extremely popular in European and Asian games, and used by disabled and non-disabled alike, Click-to-Move is when the developer allows for a gamer to click the terrain and have the character move to that position in the world. Meanwhile, Mouse-to-Move is when the designer allows for the movement of the character by pressing both the left and right mouse at the same time, using the mouse movement to steer the characters.
These two features serve different purposes. Click-to-Move allows a gamer with a strength issue to click the ground and get his character where he needs it, instead of having to press and hold the mouse buttons or WASD keys. On the other hand, Mouse-to-Move is key to gamers who do not have the arm movement to continually alternate between mouse and keyboard. Both features let players move their character where they need it, and never have to take their hands off the mouse.
An example of excellent Click-to-Move incorporation is the original Dragon Age: Origins. Depending on how you wish to control your character, you can use both mouse buttons, traditional keyboard control or Click-to-Move. This allows for gamers of any ability to control the game as they see fit.
An example of inaccessible game design is a game, which purposefully disables Click-to-Move because the community believes it allows bots. However, any program that could be used to build a bot predominantly operates by automating keyboard commands, not using click-to-move. in this situation, the game loses a useful accessibility feature for little-to-no benefit.
A disabled vet spent a lot of time playing PvP in an MMO with his buddies when he was deployed overseas. He was injured and is now stateside. He can no longer use his arms without pain. Instead, he now uses a head mouse, which allows him to play the game without moving his arms at all. He still wants to play with his buddies. In the old days he would have to use the WASD key or hold down both mouse buttons to move his character around, but the makers of the game considered these issues during development and included Click-to-Move in the title. This means he can play the game without moving his arms, and stay connected with his old Army buddies.