My pet hates:
Misuse of the phrase "Immaculate conception." It is not, in any way, synonymous with the conception of Christ. It refers to the fact that Mary was, from her very conception, without original or personal sin.
Misuse of the phrase "begs the question." Begging the question is an informal logical fallacy in which the conclusions of an argument are wholly or in part present in it's premises. It's essentially the same as circular reasoning. I does not mean "raises the question."
People who correct my (correct) pronunciation of
niche. "Nitch" is correct. "Nitch" has been correct ever since the English language borrowed
niche from the French over 400 years ago. Until the mid-to-late 20th century, "nitch" was the
only correct pronunciation. "Neesh," while truer to the French, is not the "correct" English pronunciation (except in the UK, where it's pretty much totally supplanted the original).
I may pronounce many words incorrectly, but this isn't one of them.
Just where is "Febuary" sanctioned? 
Most American dictionaries list feb-yoo‑er-ee as a standard variation.
