Best is subjective. What works best for one person doesn’t necessarily work at all for another, even if they have the same disability. However, we do have frequently used switches AbleGamers recommends over many of the others.
Ultra Light Switches
These extremely sensitive switches can be activated with the lightest of touch.
These are essentially the easy button you see on Staples commercials
These are switches in the form of a credit card. Flat, rectangular, and very smooth.