In 7th grade, I took an SAT test without preparing for it at all, it was spur-of-the-moment, I knew about it about an hour ahead of time and didn't do any research or anything. I scored higher on it than the average person using it to apply for college in my area.
An IQ test has shown me to be in the 99.9th percentile for IQ. This is the highest result the test I was given reaches; anything further and they'd consider it to be within the margin of error for that test.
I have independently thought of basically every branch of philosophy I've come across. Philosophy has pretty much gotten trivial for me; I've considered taking a philosophy course just to see how easy it is.
Psychology, I actually understand better than people with degrees. Just as with philosophy, there's no aspect of psychology which I don't have a very good understanding of. I can debunk many of even Sigmund Freud's theories.
I'm a good enough writer that I'm writing a book and so far everybody who's read any of it has said it was really good and plausible to expect to have published. I've heard zero negative appraisal of it so far; people have critiqued it, but not insulted it.
I don't know if this will suffice as evidence that I'm intelligent, frankly i don't care as long as I know that I'm more intelligent than the rest of you.
In closing, the people who know me in real life all respect me, as do a great many people in the Ebaum's community, where I spend most of my time.