My favorite Kill was in World of Warcraft when I killed a hunter (ranged damage) with a dagger thrown by my rogue (usually melee damage). Since I am undead, I eat my foes once I slay them.
Or perhaps for Tenchu: Return from darkness (which I love for its flawed AI) Both Rikimaru and Ayame's aerial stealth kills. Rikimaru jumps on the shoulders of his victim and thrusts down with his Katana leaping off before they collapse. Ayame would leap and land with one shin on each shoulder of her enemy, then she would twist her legs and snap the enemy's neck. The body would crumple forward and have a face staring at the sky that should be looking down,
My favorite death is any in the original Prince of Persia when he has a memory lapse after you're a tard and forget to rewind time.
After that I'd say drowning in Sonic the Hedgehog 2. The music, the suspense, the countdown, the chance for redemption, followed by a plummet through the ground. I know this happened in all the old sonic games, but Sonic 2 was by far the best and deserves to be credited so (though perhaps a topic for another post).