I have a boss that says, "from the gecko" instead of "from the get go". Maybe he has insurance from GEICO. He also uses "coming down the pipe" instead of "coming down the pike".

Worked in a liquor store in college with a lot of clientele that were asking for "A quart of Winston Canadian". They were asking for "A fifth of Windsor Canadian". I had a hell of time figuring that one out. A quart and liter seem a heckuvalot closer to each other than 3/4 of a liter.
...another was "Gibley's Gin". Sold a boatload of Tunderbird though.

My first wife had trouble pronouncing "hippopotamus" and it would make her seem to stutter. We settled on "Hip-mo-potus" and she was cute as hell saying it.

A co-worker's small son had trouble with "101 Dalmatians". They got one of the breed and he called it a "Dalmalmatian".