16. What is your favourite Psalm, and why?

I thought it would be interesting and helpful for me if I had an idea of your favourite Psalm(s) and why. So, feel free to let me know.
Let me start.
My answer: I guess over the years I have had a few, but in recent years it has been Psalm 13. It says:
1 How long, Lord? Will you forget me forever?
How long will you hide your face from me?
2 How long must I wrestle with my thoughts
and day after day have sorrow in my heart?
How long will my enemy triumph over me?
3 Look on me and answer, Lord my God.
Give light to my eyes, or I will sleep in death,
4 and my enemy will say, “I have overcome him,”
and my foes will rejoice when I fall.
5 But I trust in your unfailing love;
my heart rejoices in your salvation.
6 I will sing the Lord’s praise,
for he has been good to me.
It is a psalm of lament by David, which I have discovered is able to be applied to many difficult times in our lives and yet ends with a real sense of hope and optimistic faith. Why it is presently my favourite is because I have used it in recent years in encouraging others going through tough times. Together we have prayed this psalm asking God from our hearts, “How long?” and then ending with “But I trust in your unfailing love.” These prayer times have been very moving. I have also appreciated being able to preach on this and other lament psalms. More on this later.
I look forward to hearing from you.

An interesting version of Psalm 13 is sung by Brian Doerksen @ http://www.youtube.com/watch?v=_AT7wa0tPVU

A song on his album “You Shine” (2002).