I like the snark mark. Although how many people would understand it? You can say stuff like "I don't like the snark mark: ~". ~ And then people start looking for pictures in the punctuation. So I'll never use the snark mark.
An English Skills poster which demonstrates figures of speech on one side and common grammar mistakes on the other side. Would be useful displayed in a classroom for students to refer to during writing activities.
Do you have a crush on idioms? This visual is great for explaining idioms to ELL students or students who are having trouble understanding the double meanings of the idioms. This is important for reading as idioms are used quite often in writing