For years my mother, who grew up in the U.S. South, would pronounce "washer" with an 'R' as in "Put the clothes in the warsher." I've nagged her on it so consistently that she almost never does that any more.
A friend from high school was a master of mispronouncing words. "Rogue"--referring in this case to Rogue from the X-Men--he pronounced as "rog-wah".[1] He also pronounced "scythe" like "sky-th".
What words have you mangled or heard others mangle over the years?
[1] This was before the movie came out, BTW.