When is it ok to lie?

So I asked a question – what makes you angry? And during the thread a discussion started about lying; one person believing it was totally unacceptable at all times and there is no reason at all to lie and a few others feeling that in some circumstances a lie is the only option. So have you told any lies? Can you justify them? Are there any occassions where a lie (yours or someone elses) has really made a mess of your life? Or is there a lie out there that has saved your bacon and meant that you have had a better life because of it? Just curious as it was getting to be quite a discussion and felt the question needed to be asked !