I got two.

First, midlaning TF, teammate comes down to help gank Ashe; she escapes with 12 hp.
NOT. Destiny Teleport in front of her kill her on the first autoattack before she can even change direction.

Next, playing... (I actually forget who. odd) Basically, their Ez had been feeding off three of my teammates, but hadn't put anything into defense. We got his health down ,but he took cover at a turret. I snuck around back and shot him with a gunblade. SHUT DOWN.

Yeah... Those have got to be my two most satisfying kills.

Dad made me clean up something and i afked as WW for 15 secs in a teamfight. When i returned... QUADRA KILL!

My funniest death ever (since that's kind of related): I was playing Poppy, soloing top, when the jungler comes in for a gank. Anyone who knows Poppy knows that with the help of her ultimate, she can EASILY 1v2 if she is fed, so that's what I did. (most fail gank ever, lol...) After my double kill, I had about 40 health left, so I went in the bush to recall. Suddenly, Veigar (playing mid lane) starts frantically pinging "be careful" around where I am. I was almost done recalling, so I ignored it. But suddenly right before I was in the clear, ASHE ULTIMATE TO THE FACE and I died.

shaco clone getting a double kill after i died.

Here's another one.

When I was playing as kassadin, my mouse derped out and I accidentally rift walked into a bush. I turned out that the whole enemy team was in that one bush on 5 health after we ganked mid. (stupid choice for the enemy, but I was playing against four level 6's and a level 20)

PENTAKILL!!!!

as always somehow i get a bad darius on my team while the enemy darius gets fed to 13 0...he sees me get fed to 6 0 as cass, i run to the blue buff bush on blues side and as he comes at me im like w TROLLFACE ULT, E E E E E E E E.....shut down.....my team from then on thought i was a god

Playing Blitzcrank after pulling the first enemy we managed to kill him and got into a fight for 3 (my team but the other 2 players were not close to us) vs 4, I was near death but luckily I maximize my W and kited most of them causing aced for my team.

I was playing Cassiopeia and the enemy vayne got me pretty low so i started running from her to my tower but i wasn't fast enough, one more good crit and I'd be dead....so i just turned and ulted her, which killed her instantly XD