Backish Mush (Bacchus Marsh) - my kids still give me grief over it. It's how I pronounced it for the last 50 years, get over it.
Sans, as in French for without. Until my mid-20s I always pronounced it "sans" as in fans. Until some prick sfellowed at me and said it was "sonce" as in nonce. How the fu** was I meant to know, I did German at school du schwanzlutscher.
Also the cheese-eating surrender monkeys had me with svp. "I weel have le burger sans sauce, svp." I called it sivvip. Not s'il vous plaît. Ess scheisse und stirb, Frösche.
That prick was wrong. Its 'sahn'.