I have none that are fanny, but since my friend had this one I stopped using dictation all together, braille screen imput for life.
One time my friend asked her friend what was up and she said she went outside and my friend was just normally asking how was the weather there and the stupid dictation asked how was the weather in the pennis, but in Romanian.
The problem is that the words don't relate in Romanian at all, so I don't know how it did it, she didn't press send though and just sent a voice message instead.

Here's a good few, and some even expand on some of Nocturnus's corrections.
On Friday after school, BF/GF relationship.
Boy: Can’t wait to see you babe.
Girl: It’s Friday. I’m getting pregnant tonight!
Boy: Shouldn’t we talk first?
Girl: Oh my God! I wrote pringles and it autocorrected to pregnant
Boy: I almost had a heart attack!
Attempt at being gangster?
A: I’m gangster. I’m a straight up G, the hamster life is the life for me. STUPID AUTO CORRECT!!!
B: Been spendin’ most of their lives in the hamster paradise.
A: Don’t make fun of me
Woman: Babe I don’t feel like cooking. Can you bring home human beef?
Men: WTF Beth? Human beef?
Woman: I’m laughing so hard.
Boy 1: How was the date?
Boy 2: Not quite. First date we went to dinner and then I killed her in the woods outside her house and left
Boy 1: Killing her seems a bit harsh.
Boy 2: KISSED, wtf
A: Can I get my pencil back? I have an exam in 30.
B: yeah. I’ll get it out of my lover.
A: Haha. You and Dan are into some kinky stuff.
B: *Locker. Love it!
A: Are you done painting Jason’s living room yet? What’s the color?
B: Just finished. It’s called period red.
A: Dude. No!
B: Sh*t! It’s called Persian red! I got autocorrected. Epic fail!
Mom: Are you hungry? There’s a huge surprise waiting for you in the kitchen. It’s your favorite.
Kid: Starving. I hope you shaved pussy. OMG!! I meant porkkk shaved pork. It was the worst autocorrect of my life.
Q: How did Emily break her finger?
Julian:  Her finger got stuck in my butthole
Q: WHAT????
A: I’m coming over and I’m bringing cold hermaphrodites
B: Uh, no!
A: HEINEKEN!
It's not actually the easiest thing finding these, as most websites portray the information as a single image.

I've had a few auto correct mishaps crap up over the years, but here is my personal favorite. As with many of these, it is slightly offensive. Maybe more than slightly so don't read it if you're easily triggered.
I read a tweet from a blind person who was talking about his new Vape pen and how much he preferred vaping over smoking cigarettes. I dictated the following:
Can you give me more information? I'm curious how a blind person gets into vaping.
Dictation result:
Can you give me more information? I'm curious how a blind person gets into raping.
Epic fail! Proofreading for the win!
BTW, I dictated this post, so crap up should have been crop up. I left it in for a laugh.

Yeah, you really, really want to proofread your dictations. No matter what language you're using and what you're writing. The number of people who don't, and then just hit send is just insane. Applevis is a prime example where you'll see this often, but if you've been on Twitter or mailing lists you'll see plenty there also. First one that comes to mind for me is how a person on Applevis was praising their iPhone 6 ass, how much of an amazing device it was. Well that comment would suggest otherwise! . I've also seen someone on the Dectalk mailing list writing it out as "Dick talk" instead, which although I'm sure is a very interesting topic is probably not relevant for that mailing list.

As for me, I'm fairly sure I had a number of these over the years but since forgot most of them, also because they were caught before being sent. One small and amusing one that wasn't though was when I got my first smartphone and started using foursquare. Being able to dictate was such a fun gimmick back then that I wanted to do it every time even though that phone also had a keyboard. So we went to the shopping mall for lunch and to pick up a copy of Mortal Kombat 9. So, I checked in and dictated "getting food and Mortal Kombat". Fast forward a few months, I'm scrolling through my old tweets and... Turns out my check-in actually said "Getting food *In* Mortal Kombat". That would have probably been far more entertaining! XD

I never really liked DecTAlk, but DickTalk? Now I think I can get into that!

Fits very well with the bendgate issues, where users would place the phone in back pockets, only to have it bend, desoldering chips on the motherboard in the process.

I was once talking to my brother's caregiver on two separate occasions.
The first time, I was dictating a message in which I said, explain the difference between this and that, but it wrote, explain the difference between bitch and vent.
The other time, I think I said, feed him early, but it came out, please her boobies! I was totally embarrassed when I saw that the message was already sent!