Malzahar ---> Anyone: "I saw your demise from the beginning, did you see it too?"
Anivia ---> Annie/Brand: "Even fire can be frozen"

More killing quotes!

Pantheon->Darius - Getting the largest weapon you can find and spinning like a maniac does not work, stop trying
Pantheon->Draven - Ugh, the ego was insufferable. I think I enjoyed that more than I should have.
Pantheon->Pulsfire Ezreal - Your scanner is broken. My power level is far above 9000.

Jaximus > anyone: "Thumbs up!"

(for all of you who don't get it, modern movies often portray death as being a thumbs down in Rome, whereas in reality if the Emperor thumbed up the gladiator this meant that he approved the death sentence; a thumbs down meant the gladiator would be spared)

Temple Jax > Ionians: "Sorry for stealing your limelight."
Temple Jax > Noxians: "I think I'm starting to get a hang of this 'balance' thing!"

Pantheon > Leona "The first victory against Leona this round!"
Leona > Pantheon "What's wrong? Still can't beat a girl!"

wouldnt Nocturne > Leona be : I wear my sunglasses at night.

And still more quotes of champions killing themselves.

Ashe: "This is why I'm the queen of Freljord."
Karthus: "Back to the swamp with you!"
Kassadin: "I will deal with the Void myself, thank you very much."
Katarina: "Nice try, copykat!"
Sion: "I am dead. So are you. Again!"
Tryndamere: "The mighty Tryndamere has no equal!"
Warwick: "Guess we know who the alpha dog is, huh?"

Nocturne > Lux or Leona "There is always shadows, where there is light."

Teemo -> champs of normal size "Never Underestimate the Scout's Code!"
Larger champs "Size doesn't mean everything"

Zyra to Maokai: Embrace your new life Treant...oh wait...you are already dead.
Zyra to Rammus: I thank you for paving the ground for me. Now I will reward you with death.
Maokai to Zyra: Your inhumane magic is beyond words!
Nidalee to Zyra: Aw...who needs a bushwhacking?
Zyra to Nidalee: There is only room in the Plague Jungle for one transforming woman in heat.
Jayce to PFE: Your armor is outdated...
PFE to Jayce: I guess I am now the only defender of tomorrow
Viktor to PFE: You are an imperfect machine...now you cease to exist.
Jax to Draven: WELCOME TO THE LEAGUE OF JAX!!!!
Draven to Jax: The Champ is dead! HAIL TO THE CHAMP!

Shaco --> Viktor: "That robot business sure is tough when the chips are down."

Shaco --> Ahri: "Might wanna' look into retail now."

Shaco --> Cassiopeia: “'fangs for the memories."

Shaco --> Alister: "I'd milk this for all it was worth, but that would probably incur some bovine intervention and then I'd probably throw my calf out."

Shaco --> Cho'Gath: "You eat your meat live? Well, if you are what you eat I find that hard to swallow."

Shaco --> Evelyn: "Whats pink and blue and red all over..."

Shaco --> Malzahar: "Looks like this heir of the void is now void of the air."

Shaco --> Blitzcrank: "I always did find him revolting."

Shaco --> Malphite: "Just not quick enough. If only he didn't lead such a sedimentary lifestyle."

Shaco --> Caitlyn: "I'd steal your heart, but looks like you already made a cardiac arrest."

Shaco --> Nocturne: "I always was a light sleeper."

Shaco --> Maokai: "Should've packed your trunk and left."

Shaco --> Zelias: "Watch out, second-hand smoke can kill."