For a recent storywriting competition I was privileged to judge, there were some great examples of unreliable characters who kept me guessing and misdirected me beautifully. I guessed at the story endings, all sound logical guesses based on what I had read in the first page or so, and I'm glad to report I was wrong on every single one of them!!
Why glad? Because those unreliable characters had been so well portrayed, their words and actions were convincing and then they successfully pulled the rug out from under my feet right at the very end. For me, that is the very definition of what an unreliable character should be. Everything that character says and does should be perfectly reasonable from their viewpoint. There should be no extremes (they'll alert the reader there's something wrong with the character and the element of surprise is crucial).
Another character type I like are those who are convinced by their own perspective on life and have to face up the fact not all is as they would like it to be and they have to change at least some of their views. The way a character changes during a story is endlessly fascinating for me, as it should be. Characters drive the story. They must grip your reader (even if they end up dropping said reader from a great height by misdirecting them!).