Being called some names in another thread made me think of some self deprecating statements I have used for myself.
I’ve called myself a cheap ass Polack many a time. In recent years I’ve more readily referred to myself as a fat old man. And I’ve referred to myself as a Luddite more than once (tho I’m not entirely sure how much of an insult that necessarily is.)
Anyone else ever publicly insult themselves?
I frequently refer to myself as a useless artist when I say, “I have a degree in Creative Writing… that’s why I’m working in a totally different field!”
I often call myself fat, but then follow it with, “It’s obvious that I’m marrying a chef, huh?”
I often say that my grammar is a crime against nature, as English is my second language.
That being said, it is fun to almost see the brain gears of very extreme posters grind to a halt in their heads trying to process the fact that other posters agree with me after presenting convincing evidence on a subject. (Extreme posters usually dismiss the evidence and assume that others will also dismiss it after demonstrating with no effort that I have problems with English.)
But it is true; your grammar can make others, especially in this board, assume that you are not even at their level.
Oh boy, self-deprecation! That’s where I’m a Viking!
Mostly I stick with the flat-chested jokes. Got a feeling those will always be with me. 
I’m also technologically impaired trailer trash. Woo-hoo!
“Sorry, I’m blonde.”
“Sorry - Trivia is my life”
(said when I toss off a random factoid in the middle of a normal back-and-forth conversation - I’ll toss it out to see if they bite and self-identify as trivia-minded)
“Pardon my geekiness”
(said regularly during discussions that veer into work and play areas I am passionate about when I dig in a bit too deep)
When I am having difficulty understanding something being explained to me:
“If you haven’t already done so, assume I’m an idiot. Now please tell me that again slowly.”
“I’m a dumbass”
Never claimed to be clever about it…
I say that I’d be having a blonde moment, if I had hair.
FTR, what I have left is salt and pepper.
I’m sorry that I’m not attentive to your emotional needs; I’m just an engineer.
“I’m color-blind.”
I’m actually only a little bit color-blind. I’m mostly just unobservant.
Sorry about that, I’m suffering from incipient decrepitude.
I often refer to myself as a short, fat man, but only because I’m short and fat (and a man).
My boneheaded moves are generally followed with a sheepish “good thing I’m so pretty, 'cause I’m not that bright”.
I often use a partially-remembered Simpsons line, “God help me, I’m just not that bright.”
I also sometimes make joking references to my “surface-of-the-moon complexion” (As a teenager, I inadequately addressed my acne issues. Don’t be like me, kids!) In one of my friend’s wedding photographs, I appear in an odd orange light – I think it was on a dance floor. I remarked to him that I looked like an old, hammered copper pan.
When I mess something up, I ususally say, in a very sarcastic voice, “Wow. Go me.”
“old, fat and ugly”
I’m an artist; I majored in Studio Arts with a minor in “…would you like fries with that?”
When I’m at work, my favorite is “What do I know, I’m just a dumb plumber?”
Elsewhere, it’s “I’m short, fat, ugly and hung like a bull gerbil!”
Life’s too short to be too serious.
“I couldn’t have said it better myself”.
“He was a man, take him for all in all, I shall not look upon his like again”–“I couldn’t have said it better myself!”
“She walks in beauty, like the night of cloudless climes and starry skies; and all that 's best of dark and bright meet in her aspect and her eyes”–“I couldn’t have said it better myself!”