Blood Lord Vladimir's 3rd laugh
The aforementioned laugh featured in the skin's trailer: http://www.youtube.com/watch?feature...r9xDjs9M#t=34s
The laugh: http://www.youtube.com/watch?v=sMJjT...tailpage#t=67s

It's not a big sound, but the sound of Kat refreshing her cooldowns after a kill, and really all of the sounds her blades make are so... crisp? I don't know, I just know I love hearing all her different blade sounds.

Jax smashing the **** out of a tower after leveling his ult.
Eternal Noc ulting, as previously mentioned.
The hooking sound Leona's Zenith Blade makes when it roots a target for her dash.
The cast sound when Malz drops or bounces a vision between units.
And pretty much every single sound on Arclight Varus.

I like a lot of the sounds from pulsefire ezreal :P

Teemo's voice over for his death

The sound of 25 mushrooms exploding on 2 enemies chasing Teemo down the river

Eternum Nocturne ult.
Draven
Getting hit with a Nidalee Spear

Karma's death cry
Start up of Morg's ult
Flash ulting somebody as Cassiopeia from the fog of war, cus you know they just crapped themselves

HIEEEEEEEEEEEEEEEEEEE Laz0r