Let's see...
The last lie I told was earlier today (or yesterday, I guess) to a rather friendly telemarketer who was asking me if I was enjoying the beach where I live, as I am on summer vacation. I have not been to the beach in several months, possibly a year, but I told him otherwise, so I would not scare him off with my abnormality. I am too polite, sometimes.
The greatest lie I've ever told about myself? Well, I guess I have a couple of those: I once said and maintained lies like that I have the ability to teleport over great distances, that I am the leader of a paramilitary resistance force hidden in northern Scotland that works to lead a rebellion against Great Britain and establish Scotland as a sovereign nation, and then conquer Norway, and that I am actually a god of death in mortal form. How about
that?
The longest lie that I have ever maintained is one that I am going to stop maintaining right now. I have brought it up at every appropriate opportunity that my great-great-great-something grandfather was the legendary James Watt (He's the Scottish engineer who perfected the steam engine, thus kickstarting the Industrial Revolution, from whom we derive the unit of power. Did I tell you that he's my great-great-something grandfather?

).
As far out as these are, they're usually said somewhat facetiously. My little brother, on the other hand, is the bad kind of liar, the one who lies to get his way. After a week in drug rehab, he kept on saying that he had given up on drugs. Apparently, he's very good at lying, for when he got back home he announced that his plan for his life was to continue smoking marijuana until he was 18 or 20 or something. He's quite manipulative, and there have been times in the past when he has denied wrongdoing up and down until we were convinced, only to admit his crimes when the heat was off.