Browsing around imgur, I can't find a way to get rid of my account.
The Terms of Service say, "Don't upload copyrighted material, harassment, spam, gore, pornography, or especially child pornography. If you do, we will ban you, delete all your images, report you to the authorities if necessary, and prevent you from viewing any images hosted on Imgur.com."
So, I suppose you could try uploading some gore?
SERIOUSLY, though, just use the contact form and request deletion. I'm sure they get them all the time.
Go to your account in the right hand corner
Find the setting and click on it
Near the bottom towards the right there is some linked text that says "Delete my account"
Simple click on it hit the checkboxes that show and delete both your account and all of your images.