The one that drives me crazy is slider based checkboxes. I never know which side is on/off. Bad UI convention.
And speaking of checkboxes, I want an actual tick mark (checkmark), not a X cross. Its called checkbox, not Xbox or crossbox, it has to be a checkmark. Also, its a square, not a box. Disaster.
Those toggles actually mimic real hardware that used to be fairly common. I find those should be preferred over checkboxes for anything that takes immediate effect. If they don't, and you're collecting a bunch of options at once, in a form, then use checkboxes.
unless the colors are red and green, and the user happens to be red-green colorblind. So yes, always have text indicate on/off as well.
For instance, my old stereo has push button toggles, where “in” means “on” (this convention was common because of how those switches work), and three way levers with labels on two of the three positions (there’s no space to label the middle position, and it means “default”.
Relying on color to make something easy to parse is an awesome accessibility choice.