What sends shivers down your spine when you play it on your system?

The Adagietto from Mahler's 6th.

Oooo Mahler! Lots to revisit there!

Is that Mahler symphony 6 or 5?

I have that from Symphony 5 on a Classical
music for yoga and meditation CD. Giving it a streaming now.  Quite lovely and mellow yet encompassing. 

Mahler Symphony #3 is my favorite of the ones I know well. It transports me to an alternate state of mind throughout its duration.

Debussy's Deux Arabesques performed by pianist Philippe Entremont on a lousy-sounding old Masterworks LP.  The choral movement of Mahler's Third on an I-wish-it-sounded-slightly-better Jascha Horenstein recording I have  on both Nonesuch and Unicorn LPs.  Des Knaben Wunderhorn on Vanguard. Mike Garson's piano solo on Bowie's Aladdin Sane.

I think twoleftears meant Mahler 5, which I agree is absolutely beautiful.  Staying with Mahler, I agree with Mapman on Mahler 2, the final portion of the last movement always gives me the shivers.  As does the third movement of the Shostakovich 5th Symphony.