The word "mobile"? (As in, the thing that hangs in the nursery about the crib or changing table).
I'd never had a reason to say it out loud before, and when I did, my husband gave me a funny look and told me I was saying it wrong.
How do you pronounce it?
ETA: I pronounced it "Mo-BEEL" and DH insisted it was supposed to be pronounced "Mo-BULL"