I love the following songs:
Lift up Your Hands to God
Imagine Me Without You
The Prayer
Healing
We Are The Reason
Let There Be Peace On Earth
Here I Am Lord
Here I am Lord
Agnes Dei
I really like Ave Maria.
Schubert’s “Ave Maria”
Gounod’s “Ave Maria”
My all-time favourite has to be Allegri’s Miserere. It’s so evocative, it’s like a little sumptuous morsel of the life to come.
Not exactly a spiritual song, but I like the message in You Can’t Always Get What You Want by the Rolling Stones. 
Wow! I was just singing…
The Summons - Robert Kochis (Album: You Are Near)
The first time I heard it was in November in RCIA. Our Pastor makes us sing a couple of songs every class. When I heard it the first time, it made me cry. It was calling out to me!
I went home and found it on iTunes and listen to it almost every day.
Another one he plays a lot for us that I absolutely love is Hosea (come back to me). The one by Steve Bell on Suns and Daughters is wonderful
Tops on my list: The Galilee Song
Tis Midnight on Olive’s brow
Why not tonight.
As a deer
Ave Maria
How Great Thou Art
Jesus Christ Is Risen Today
Now Thank We All Our God
Humbly We Adore Thee
At The Cross Her Station Keeping
O Come All Ye Faithful
Silent Night…and many more
The Summons
Adoramus Te Christe
Immaculate Mary
and my absolute favorite…
Be Thou My Vision