Well, there's the recent example(s) of me killing a Pilot who's rodeo'd my Titan by detonating a satchel charge I'd placed on my Titan's back prior to hopping into it. (it's always a surprise and has garnered me some pretty hateful comments in chat. >
)
There's also the time I fired a grenade (from a launcher) in the caves map in Goldeneye, only to have said grenade bounce around literally the entire map until it happened upon my friend's face. To this day it remains a feat I've never been able to repeat nor have I seen it elsewhere.
There's the Mr. Saturn kill I got years ago on Smash Bros Melee. I threw him at someone attempting to get back to the stage. But instead of just hitting the guy and bouncing off, the Mr. Saturn kepting pinging off of him, effectively forcing him away from the stage and down into a KO.
There was also the recent kill in Left 4 Dead 2 that came about from a Tank rock toss in the second chapter of Dark Carnival. I was near the back corner of the bottom of the slides and the survivors were spread out from the top of the slides to the back of the other roof near the ladder. I managed to toss a rock that cleared the sliders, passed trough the railings, and landed right in the chest of Coach who was near the back roof. (of whom was black and white and attempting to heal at the time) He died instantly.
Though one of my more recent favorites was in Dota 2. I was being chased by an enemy hero, down mid on Dire side. We were both fairly low in health; me especially so; and relatively low on mana. The Sven chasing me was seconds from being able to cast his stun, and I knew I couldn't outrun him or stay out of range. So I started moving towards the trees on the bottom right of the mid lane. As he followed me into the trees, just as he popped into my line of sight, I used my Force Staff on him just before he could cast his stun. I managed to shove him right into the Roshan pit wherein Roshan attacked him - landing two back-to-back bashes - and killed him. (not technically my kill, but I thought of it as such)