You'd probably put that big sword of yours to good use.

Using the shadow behind you as a distraction, you slip behind me and using your REALLY strong and durable hair like a piano wire, strangle me.

You'd use some sort of black magic to kill me.

My hair is so strong I can kill people with it :D

Late at night,
quiet as a shadow,
A knife to my throat.

Edit: Well, I don't see any knives on you actually, but there's probably one somewhere under the clothing.

By choking me with those long, brown tresses.

They would toss me up into the sky, and command the weather to do its worst - lightning bolts, sunburn, snow, rain... You name it!

Not wanting to get your beautiful dress dirty before the ball, you sic your flying dog on me. However he is not the one to kill me. Your napkin swan waddles over and slowly suffocates me while I bleed out from the dog attack. My last view is a wicked grin across your face and my finger bones being chewed on by your dog before your swan pecks my eyes out.

*apologies for going extreme, it's just what popped in my head XD*

OMFG, so awesome! I am going to use that as this looks story, if that is okay? :3

You'd lure me in with your charm, to your place, the one in the water. I'd be mesmerized, and follow your every wink.
In due time, you'd ask me to drown myself, your face lit up by glee as the final bubble reaches the surface, and my corpse becomes one with the sea.

Um. Toxic candies. Wait, I'm not a big fan of sweets. ...Toxic ice cream?

That bad-ass custom-made stun staff

I think it's actually some sort of plasma cannon. ...Not entirely sure.

You'd probably hack into my systems and overload something or another.

I believe you would kill me mercilessly and without question.

....That's another spin on "how". (I'm quite the opposite in games, though.)

That night sky? That's an illusion. Those "stars" are actually clusters of nanoviruses, capable of entering a victim's body even through armor, much less skin. Once inside, they take over the victim's brain and nervous system, altering its very thought processes and enhancing its abilities. The result is not a mindless husk or a pawn trapped inside their own body, but rather a perfectly willing and cooperative soldier ready to work towards Glitch's goals.

o.O Espy could either shoot me with that huge ass gun or just knock me out by hitting me in the head.

I saw the skulls at your feet before I saw you. The smoke is so thick the only thing I can see is the light of your eyes as your balloon drifts over and gently strangles me, silently.
I literally NEVER saw it coming

I can see SparX using the will-o-wisps to guide me through her watery land...only to drown me. That, or using music. Either way, she'll make me Ophelia.