The click of pool balls. I never realized how much it meant to me until I tried playing with earplugs in (due to the propensity for some bars to play their jukeboxes LOUD) and the dead sound was so freaking me out and I couldn’t enjoy the game.
The sound of Diefenbaker begging for a cookie. Dief is a husky mix we got from the pound and she does this little singsong ululation that cracks me up. I can never resist it and just have to give her a cookie then.
I’m mostly deaf and never thought I’d miss sound much if I ever lost my hearing completely but now I know better.
Even though I’m strictly broadband, I still love the sound of a modem handshaking…
My favorite sound, though, would have to be the sound of Flash, my sixty-pound lapdog, sighing in my lap as he relaxes.
Breaking glass
Advancing thunder (So, Arden how YOU doin’?)
The click of excited running puppy toenails on a Pergo floor.
The tinkle of brass shell casings on a concrete floor
The sound of a magazine sliding into my Beretta
The whirr of my CD drive
Taht sighing sound a drip coffee pot makes as it finishes brewing
The little harruuuuum sound my girlfriend makes as she snuggles into my chest before falling asleep
The sound of road noise from my front yard. It’s about two blocks away from a main street; so the sound of the cars is just a really faint white noise.
For some reason, the far away sound of a fire engine’s siren makes me feel safe, secure, and happy, like all is right with the world. It doesn’t make any sense, I can’t explain it, but there it is.
Thunderstorms arouse me, too.
And why is it that a bunch of crickets chirping is a relaxing, homey sound, but a single cricket chirping can keep me awake for hours, hm?
The whistling of a tea kettle, of course. 
Way cool. Being such a thunderous bunny, (and you know what they say about us rabbits!) I’m quite overjoyed to hear this!
As for cool sounds:
Gentle rain
Snow falling (it’s very quiet, has to be out in the woods)
Cicadas in August
The sound of thick mud as you walk through it
A glass harp
Those voices in my head telling me to write weird things.
Glorph! Glumph! Icki Icki Tang Tang!!