The scythe is one of those weapons you rarely see used, but is kinda awesome when you do. My current personal favorite was seeing a mute Amish farmer take on zombies with one in Diary of The Dead.
Of course, the reason it’s used seldom is mostly because it’s an agricultural tool and not a weapon. But then again, a lot of weapons began that way (see the machete, kama, morningstar, axe, ect.)
Your average scythe is around 6′ long, with a blade 2′-3′ wide emerging perpendicular to the handle. It’s invention lies somewhere in antiquity, and has spent far more time as a symbolic weapon in the hands of the Grim Reaper than in those of mortal fighters.
In it’s usual form, the scythe has some pretty hardcore disadvantages in that you can’t attack directly at full extension. Even when facing an opponent in front of you, a slash with the scythe using the handles “normally’ would mean a thrust with the blade at an opponent’s left side. That said, the blade’s inward-facing edge would make for a powerful hooking slash if you managed to get past an opponent’s parry or shield.
On occasion, the scythe would be modified to have the blade extending directly from the handle, making a polearm called a war scythe. Having a peasant uprising full of farmers who were used to swinging such things for hours on end had to suck mightily.
And just to clarify: The last few episodes of Buffy: The Vampire slayer features a weapon consistently referred to as a scythe. It’s actually a battle-axe with a single axe blade and head & pommel spikes. The design makes it look like it began life as a heavy metal guitar. Still awesome, but not a scythe.