my peeve lately is I vs me.
Tina and me looked at the llama <--- wrong! you wouldn't say "Me looked at the llama."
Tina gave french fries to Jake and I <--- wrong! you wouldn't say "Tina gave fries to I."
Nominative vs. objective pronouns are something a significant portion of the population no longer understand. The problem is particularly bad with who and whom.
Affect and effect really set me off. Particularly when someone operates under the misconception that "effect" can only function as noun. For example, I can correctly state the introduction of the Axe-FX has effected a change in the way many guitarists view modelers. However, many people who half understand the guidelines would insist "affected" would be the correct verb to use.
Sorry for the total derail. If any forum strives for correct usage, it should be this one.