I have too many pet peeves about words and phrases to list here, but I'll list a couple.
1. I hate it when people mispronouce the word "nuclear". It usually comes out as "noo-kyoo-lar". News reporters on TV are among the worst who can't say it correctly. It's "noo-clee-ar".
2. In the written language of today, I cringe when I see "wah-lah", used when showing something, such as "Wah-lah, here's my finished quilt." The word is voilą folks!