What's your favorite instrument to listen to?

Just love a heavy well produced guitar riff. Might be a boring answer but that’s the one for me.
- I'm also fan of a particular type of guitar riff that I can only describe as "crunchy" with my limited music vocabulary.
  The best example I can give is Spirit in the Sky. The lyrics are cheesy, but damn the guitars are fine in that track.
  
  You might be thinking about a sound with a lot of distortion
  
  I feel like Moist does amazing crunchy but melodic riffs personally
  
  To this day, nobody knows how they got that unique guitar distortion sound in that song. It's been long-forgotten, even by those that were at the session.
- Sometimes stuff is just popular for a good reason. I love loads of different styles of guitar, but I think my favourite heavy riff is probably the chorus one starting at 2:02 in Saor's Children of the Mist
  Or maybe Flying Whales because, I mean, it's Flying Whales
  
  The intro to Power by KMFDM and the intro to Sold by Imperanon are two of my favourite riffs, but I love all kinds of heavy/death metal and industrial and hardcore punk rock and classic rock. Just gets my testosterone going. Makes ma ballz buzz.

I love a good piano piece.
One of my favorites: https://youtu.be/zucBfXpCA6s
- Her Hungarian Rhapsody performance is my favorite!
  
  Ooh.. I will have to check that out! Thanks for the suggestion.
- That was a lovely performance! Great pick, thanks for sharing it

Like as the main or only instrument in a song? Probably Spanish guitar. See "Vamo Alla Flamenco" from Final Fantasy 9. I wanna say Diablo 2 had a good Spanish guitar track too, but no idea what it's called.
- I believe the song in Diablo is called "Tristram". Excellent classical guitar song!
  
  It's also a really fun song to play. I used to know how to do the intro when I was younger. https://www.youtube.com/watch?v=Q2evIg-aYw8

Drums in music. I always zero in on the percussion patterns.
- Here’s one I enjoy a lot.
  https://youtu.be/wgDZrFG8Ku4
  I also recommend checking that whole album out. It’s great.
- Tell us one of your favourites so I can look it up
  
  The first thing that pops into my head (because I recently watched it) is Chad Smith just winging a song by 30 Seconds to Mars. https://youtu.be/HMBRjo33cUE when he played it, he just felt the music.
  A bonus song that I just love listening to because of the layers is like an opera heavy metal song called Awakening the Centuries - https://youtu.be/VvYRYCIAKZo

Roland TB-303. It's the synth that launched so much electronic music. Examples are legion, but one of my favorites is Psychic TV "E-male:" https://youtu.be/o2U3joQ9oFI
Generally considered among the penultimate 303 examples are:
"Higher State of Consciousness" by Josh Wink (https://youtu.be/NdaqXjDtXkQ)
"Acperience 1" by Hardfloor (https://youtu.be/Un4CeV_l3pI)
- I was just going to say synthesizer but if we’re being specific the TB-303 is the king, especially with some real dirty overdrive

Hurdy Gurdy
- That's my favorite instrument's name to say.
- Ever listen to Eluveitie?
  
  Gave them a shot, but they're just not my genre. Thanks for the recommendation though! My partner is more into metal and stuff, so I'll pass it on.
- Holy shit I didn't know a hurdy gurdy could go that hard.
  
  It is an electric one, so a bit of an advantage over wood and string. The drone string is also doing a lot of lifting. Drones make almost any instrument better

Saxophone
- I like this one: https://www.youtube.com/watch?v=MrD05HVGVIQ

The hurdy-gurdy is so pleasant to listen too. I love the drone notes it can play.

Oboe. Anything from the Dream Academy albums would qualify. It has a nice pure sound almost like a vocal.
In second place would be the sitar, or the Hammond Organ if someone is rockin out. The Peddlers, or Fanny would be good examples of excellent Hammond.

Man, I love me some guzheng nowadays.
- There's a YouTuber called Mo Yun who does wonderful guzheng music, including some frankly mind-blowing covers of popular songs. Every so often I just let her entire channel play in the background while I go about my day.
- I also love the erhu like the Butterfly Lover's Concerto.

Piano. Chopin, especially Raindrop.
https://youtu.be/6OFHXmiZP38
If I said guitar, I'd point you to this song, which is actually a piano song performed on guitar. Lately this is the song that makes me feel things.
https://youtu.be/fnymlUUomKI

oboe, cello, violin...

Bassoon or oboe... Maybe it's the double reed?
- El Camino Real by Alfred Reed has a nice oboe solo.

Piano.

Yamaha DX7

Pipe Organ
- I would love to learn to play the organ if I had time.

The Cello, loved it so much that I started learning to play it at around 30.
https://youtu.be/7_8yPpCjK_w

My actual favorite is electric guitar followed by violin, and I'll gladly expound, but those have already been mentioned.
So for this comment I'll go with handpan drum. Those sound so amazing and soothing to me.
- Damn I've been trying to find out what the hand pan drum was called for so long, thank you haha.
  I would call it the 44 gallon xylophone

Love me a steel drum. No other instrument can instantly transport you to a beach
- Same with me. They just embody relaxation and good times. Makes me smile when I hear steel drums.

I love the theremin! This is one of my favorite duets.
- Oh wow, I don't think I've seen one played for real before! This is cool, thanks for sharing

Who doesn't enjoy some good theremin
https://youtu.be/9qYndeST4aw

If you just keep it to the basic instrument drums probably.
If we are allowing it then a heavily distorted guitar tuned stupidly low. But is it the instrument or the various electronics that make the sound?

Violin! Especially when they are used to imitate the sound of wind. My current fav examples of this: https://youtu.be/U0TXIXTzJEY https://youtu.be/NqAOGduIFbg

Accordion, dammit Accordion!

Hang drums sound beautiful

I love a lot of different instruments, but I fell in love with the Erhu after ATLA. Second to that, the orchestral strings like the violin, viola, cello, etc. Scores from Halo and Elder Scrolls franchises.
Finally, the collective vocal cords of choirs.

Hammond B3. Mmmmm.

Stylophone is very nice. The abrasive overtones are an acquired taste, but I've acquired it. It has a nice, rounded sound while not being generic like a sine wave.

I love horns in music, especially the trumpet. It's why I'm a big fan of Cake, they have a prominent role for the trumpet in a lot of their songs. The best has to be the trumpet solo in Italian Leather Sofa (starts around 2:10) but they have other great ones too.
- Cake is such a unique band. Thanks for mentioning it!
  Their covers are amazing for a cover junkie like me
  
  Yeah, I love their covers too, and I'm normally not much of a cover fan.

Classical guitar, here's Nocturne by Chopin.

When I think of a classical instrument, I think cello - specifically this piece Shadow of Doubt by Yoko Kanno, where it has such a brooding tone and power.
Being a synthesizer nerd, I like those most, but they have such varied tones among them and even on the same synth; 4x Atlantis by Aphex Twin probably captures one of the tones I most love, and the entire "Orphans" piece hits much of the range.

Violin is up there for me, such rich notes and emotion can be pushed through it.
After that a didgeridoo played well is awesome. I like to play mine into the bath tub so I get the reverberation and can really hear it

Sitar!

Bamboo flute!

I really like the duduk.
https://www.youtube.com/watch?v=Ubg7AI81VsQ
The most well known piece is probably the gladiator music.

I'm not normally a big flute fan, but the flute solo in Locomotive Breath by Jethro Tull is fire.

A cozy EP, one that you can usually hear in jazz, fusion, and r&b.
An 8-string guitar with a clear heavy djent tone, like Meshuggah, Tesseract, and Animals As Leaders.

Saxophone. But not always because it's smooth. Because sometimes it ROCKS...
https://youtu.be/7QFNAtnUDJ8
...Or because it's crazier than anything you've ever heard!
https://youtu.be/BARAHLk-8dk

I dunno about favourite but Kamancheh sounds pretty lovely
https://www.youtube.com/watch?v=R6D_3sBN3FM&t=224

I'm big fan of pianos (but not all piano genres) and I have learned that I really like piano run through a phaser and doubled with a Japanese koto

Harpsichord. Its just such a nice and unique timbre

Native American flute.
There's nothing that makes me chill out and vibe faster after work.

Chainsaw (bfg division)

I appreciate a good bagpipe. Especially when they share a lot of tonal similarities with violins like this nightwish instrumental. https://youtu.be/yOxGlXmPusI