Take a look at the accessibility features. With Mouse Keys, you can control the mouse with the keyboard including clicking on the mouse by pressing a key rather than the mouse button.
On newer Macs, you can also click and move the mouse based upon facial position and expressions. On my wife’s new iMac, I was having fun using just my eyes to move the mouse, and clicking on it by sticking out my tongue.
You can also use the tab key, space bar and return key to handle dialog boxes. Use tab and shift-tab to highlight the right button and space bar to click on the selected button. Or press return to click the default highlighted button.
Enable Head Pointer: This allows you to control your mouse while moving your head. You can set it up where the mouse moves where you look or moves when you look at the edge of the screen.
Enable alternate pointer actions: This allows you to control mouse clicks with facial expressions or assign alternate keys.
Clicking on the + allows you to assign new facial expressions to particular clicks. Pressing the circle with the ellipsis allows you to use switch controls. For example, I can assign the F1 key to a left click.
Facial Controls. Sticking out tongue to do a left click. (Or blink, lip pucker, nose scrunch, or smile).
It’s a fun thing to play with and I’m very jealous.