Obviously pets don’t count, since my cats lie to me all the time. And political lies don’t count, since the field is so rich.
The lies I tell to myself, which are too numerous to list. 
But I am going to lose that 20 pounds, again.
If you want you could grow up to be president some day.
When I was a kid, my dad told me the South had won the Civil War. Not just in passing, but like it was Gospel History. He had me so convinced (your dad wouldn’t LIE about a thing like that, would he?) that I’d defend him and argue with kids at school. This was his idea of teasing/humor.
To this day, I hate teasing of any kind that makes someone look stupid. Not funny. 
My dad once had us get up early on a Saturday to make signs welcoming the President (I want to say Bush) since he’d be visiting the neighborhood. I was 7. Har de har.
My roommate freshman year in college was a pathological liar. I never could figure out if he actually expected people to believe his crazy stories, but by age 18 he had allegedly:
- Flown commercial airliners for TWA
- Flew rescue helicopters for some search/rescue outfit
- Scuba dived on a Jacques Cousteau expedition
- Worked on a drilling rig off the coast of Libya
And those are just the stories that have stuck with me after 40 years. There were plenty more.
“… with liberty and justice for all.”
In God We Trust
I knew a guy like this in high school. He expected us to believe his father was a test pilot for flying motorcycles used in top-secret missions during the Vietnam war.
Many years ago, my brother related a tale to me about a blatant lie someone told him. It was just when Stereo TVs were becoming a thing, and being in the market for a new TV, he went looking for a stereo TV.
He was looking at the one the TV salesman told him was a good one, but then asked the salesman, “Are you sure this is stereo?” “Of course it is, why do you ask?” “Welllllll…it’s only got one speaker.”
Salesman: “You only need one speaker for stereo!”
My brother did not buy it. Or the TV 
I had an employee years ago who told whoppers. I assume she was mentally ill. She told everyone she owned a big jewelry store in Georgia (her birthplace). The store did very well, but she didn’t take any profits, they went to the poor kids(?). Meanwhile, she would eat other people’s lunches because she was struggling financially.
A technician who reports to me lies all the time. He’s notorious for calling in sick when I highly doubt he is. There was one time he called in sick, and his name was tagged in a Facebook photo on the same day. The photo showed him playing golf with a friend.
A few years ago I posted a picture of me and some friends on Facebook. We were at a bar at 3 pm, having a good time. One of the guys cellphone rang. He ran outside to answer it and told his wife he was at work. She had seen the Facebook picture, so he was busted.
They got a divorce a short time later. I felt awful, but we are still friends.
When we were about 18, a guy I vaguely knew (friend of a friend) explained that he had designed a car engine that only consumed water, but that his plans had been bought by an oil company to keep it off the market. I thought it sounded fishy but I didn’t know enough about physics, thermodynamics, etc. to blow him off (this was the mid-1980s, no Internet).
Certainly not in terms of the magnitude of the lie, but in terms of unbelievability…one of the employees of a department I managed years ago used to call in sick often. To the point where he’d burn through his designated sick days early in the year and start working through his vacation days.
I understood and didn’t mind too much, since his wife also worked and they had two small kids. But, every single time he called in, it would be like he was on death’s doorstep: “(strangled, hoarse whisper) hey solost, (cough cough) I’m really sick. I can’t (cough) make it (cough) into work today.” Always the same terribly acted, completely unconvincing performance. I almost had to force myself not to laugh as I played out the charade, saying “ok, hope you feel better soon!”. I wanted to say “look, just say one of your kids is home sick from school and it’s your turn to watch him. Or say a family thing came up, I don’t need to know more. Or even just say ‘taking a personal day’. I really don’t care”. But that would just have made us both uncomfortable, so the fiction played itself out every time.
Of course, the next day he’d come in perfectly fine. “Feeling better?” “Oh yeah, just a 24 hour thing”.
Around 1991, I absolutely convinced my college roommate that my parents had an awesome, fancy new microwave that also functioned as a flash freezer. I had him believing I could make a tray of ice cubes in 30 seconds. Hook, line and sinker.
One of the worst lies I was told was one time I was arresting someone, and while searching them after they were cuffed, I found drugs in the guy’s front pants pocket. When asked about the drugs, he told me he didn’t know anything about them, and that they were not his pants. He was just borrowing them.
“Hey, if any of you don’t like it here, you can leave at any time, it’s a voluntary program.”
Most unbelievable?
“Those drugs aren’t mine. I saw them lying on the sidewalk and I picked them up and put them in my pocket so I could throw them in the garbage.”
When my siblings and I were at the tooth-losing age, my father would tell us that if you lost a tooth and never stuck your tongue in the hole the tooth left, a gold tooth would grow back. But if you ever stuck your tongue there, even once, a normal tooth would grow.
It was so bad, I used the same lie on my kids. 
One day in the garage, I watched my husband getting out of his car. As he opened the car door, it dinged my car parked right next to it. I said,
“Hey, you dinged my car!”
“No, I didn’t”.
“I watched you do it just now!”
Silence.
He saw me standing right there watching him do it, and he wasn’t trying to be funny or devil-may-care cocky. It was more like he was on auto-lie.