What are some words you’ve accidently said? what did you actually mean?
I’ll go first, Frain bog I mean Brain fog
My husband has a tendency to say one word or phrase when he means another.
My favorite: “We have to put our butts to the metal.”
When I was young, I read a lot and didn’t always know how words were pronounced. One day, I told my mom about two things that were very “sim-IL-yer”, when I meant “similar”. She laughed about it for years.
Yeah, I didn’t think it was funny either. 
Ha ha, I RoonerSpism all the time.
Hopefully on purpose… I hope I’m not getting DiseaseHeimers’s Altz…
I remember embarrassing myself in front of my smart friends in college when I said “EP-i-tome” instead of "e-PIT-o-mee
Look, most of my vocabulary I got from reading. To this day there are words I’m not sure how to pronounce.
Saw one last night. “Oeurve.”
(ETA: you should see my husband try to remember how to pronounce “noir.”
I finally said, “nuwar. You know. Like nuwarwhals.”
I really cracked myself up with that one.)
My uncle, accepting a dinner invitation: “We’ll be there with bells and whistles!”
Yeah, me too! 
I thought Calvin’s tiger friend was named Hobbles when I was a very young reader and still sometimes doubletake.
My wife often calls it Amortizer’s Disease.
For an embarrassing length of time I thought that “epitome” was pronounced “epi-tome” and that it meant a very thick book. Yes, seriously.
Not me, but I had a close friend recently respond to my wise-ass comments by saying, “Don’t be so smuckin fart!”
I once got into an argument with my 8th grade English teacher about the pronunciation of “celtic”. Being in Maine, she went with the way the Boston team says it, I countered that the real Celts said it with a hard C. I didn’t do well in that class. Granted, at that time in my life I was a little PITA.
I also had trouble with “hyperbole”, I mean it sure as heck looks like “hyper bowl.” And I agree with @Chefguy on epitome.
I had a co-worker who naively prided himself on being “worldly wise.”
We cracked up when he reported he had been to party where they served “CRUD-ites.”
I won bets from him at various times, on various subjects. For instance, he insisted that Bruce Springsteen (rather than Tom Waits) wrote “Jersey Girl.”
Another time, he insisted that sharks are mammals. That one took a call to the New England Aquarium to straighten out. More $$ in my pocket. (The guy on the other end of the phone finally said, “Who IS this, anyway?)”
I had a friend from Lubbock, Texas who once bragged that he grew up down the block from the store where Billie Holiday bought his first guitar.
That reminds me of the time I took a riverboat ride in New Orleans. Upon disembarking, a woman said to her friend, “that was fun, they had a kaleidoscope and everything”.
(She meant “calliope.”)
I knew the word epitome, but had never seen it in print and spoken at the same time. If someone had asked me to spell it, I’m guessing I would have come up with “epitomee” “epitomie”, or some such.
For the longest time I mispronounced “chipotle” by transposing the final two consonants. In other words, I said “chi-POLL-tay” rather than “chi-POT-lay”.
I also kept calling the Intel Xeon processors “xenon”, like the noble gas.
Kind of hard to express in English, but I had a major gaffe at a group of Chinese college students when in the middle of a sentence, I meant to say pei chan (“compensate”) and instead said pei zhan (“to be buried with someone.”) There was a few seconds of stunned silence, then horrified laughter.
Oeuvre - not that that makes it any easier to pronounce!
Dammit. I checked that twice!
I would love for a little pop up dictionary on my phone that didn’t require swiping to another page.