Most achingly-beautiful music

Schubert G flat major Impromptu
Mozart Clarinet Concerto 2nd movement
Beethoven "Spring" Sonata for violin and piano 1st and
2nd movement
Lauridsen Lux Aeterna
Allegri Misere
Grieg Piano Concerto 2nd movement
Beethoven Violin Concerto 2nd movement
Schubert Die Schonen Mullerin final song
Strauss Four Last Songs
Vaughn Williams Lark Ascending
Somei Sato Birds in Warped Time II
Korngold Die tote stadt
Wagner Liebestod
Mal Waldron/Eric Dolphy Warm Canto

Not sure if the most achingly-beautiful music,
but a few pop songs that will bring a tear to my eye:
Peter Paul & Mary - Where have all the flowers gone
Stevie Ray Vaughan - Life by the drop
Smashing Pumpkins - Rocket
The Beatles - Blackbird

The slow movements from the Shostakovich 5th Symphony and Violin, Cello and Piano Concerti. He had a special knack for writing these movements.

I am exploring the Dvorak "Cello Concerto", I heard it performed live on Sat. night by The Haddonfield (NJ) Symphony with Mark Kowsower as soloist. Wonderful music.

Slipknot you may want to check out Jacqueline Dupre's version on EMI Mfg's Catalog # 47614
Highly Recommended!