They call it a scythe, but it doesn't look like any scythe I've ever seen. I always suspected they called it a scythe more for the metaphoric aspect of a scythe. You always see "Death" with a scythe. When you look at mystic explanations of representations of death such as in the tarot, death also represents rebirth.
OK, now on fanwanks, I might be playing with the definition a bit. Here's the definition the way I first heard it from Wikipedia -
A fanwank is an attempt to explain or justify (often through convoluted contrivances) plot holes or continuity errors in a work of fiction. The term is used both as a verb and a noun; the practice is sometimes known as fanwankery. It is disparaging, equating the activity with the ineffectual and solitary pleasure of masturbation ("wanking" in British slang).
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I remember I heard a good one one time where a guy was trying to explain scientifically why a vampire couldn't see his reflection in the mirror, yet you could take it's picture. He postulated theorized particles of light, which he invented a name for.
In what you're describing I'd say it isn't really a fanwank until you start to explain exactly how the process of "turning the scythe on", and channeling it's energy works.
I'll give you an example of what I'm talking about when I mention fanwankery with my theory of "the scythe as conduit".
In Get it Done they tell us the source of the slayer power, and Buffy's truest strength is either in, or linked to from the Shadowman's cave. The way we saw slayer creation described you have to in some way put that power into the slayer you're trying to create.
So in Chosen they want to imbue multiple girls with slayer power. Now to me that means you have to somehow get the power from the Shadowman's cave to the slayer's. Also in Get it Done, Willow and Anya say you need a conduit to transfer energy magically. I say that's what Willow does in Chosen. She uses the scythe as a conduit, and channels slayer energy through the scythe, from the Shadowmens' dimension to the potentials.
Now to me that's common sense, but apparently others see it differently. They either see Willow as in some way creating the slayer power herself using the power of the scythe as some kind of spark, or drawing the power directly from the scythe. Because there are different interpretations of the same event, I have to call my interpretation a fanwank.
Oh and here's something you might want to recall for your fanwank if you ever create one KD. Another thing Willow says in Get it Done is "Magic works of physics".