What are the best ways to implement a scythe build in 3.5 with core races?

[SangoProduction]

Races are the only thing that are core. Everything else is free game as long as it's been in a published book of 3.5. 3rd party or not.
Martial classes preferred, as I don't care for the tier system.
I've been thinking a crit fisher-type build would possibly work the best, but most of what Ive seen for crit fishers are flat increases to the multiplier, and multiplicative multipliers to the crit range, meaning a crit on 20 for x4 doesn't get as much benefit as a crit from 18-20 x2 for a base. But, I've not read all the books, so I could be wrong.

[Troacctid]

What you really want is a coup de gras for a guaranteed crit. If you can paralyze them for just a round, that's all you need.

[SangoProduction]

What you really want is a coup de gras for a guaranteed crit. If you can paralyze them for just a round, that's all you need.

Quite, but there aren't a ton of ways to paralyze for a non-spell caster.

[Grod_The_Giant]

Disciple of Dispater 8. DoD is in the BoVD; its most useful ability is (by 8th level) is to triple your crit range-- which explicitly stacks with Improved Critical. You can get in starting at 7th level, at the cost of one crappy feat, one you probably took (Combat Expertise) and one you definitely had (Power Attack). Otherwise, just build your standard Power Attack/Leap Attack/Shock Trooper murder machine-- I recommend starting with Whirling Frenzy Spirit Lion and (normal) Wolf Totem barbarian 2 to get pounce, improved trip, and an extra attack while raging, but that's just me.

EDIT: Something like Human Barbarian (Spirit Lion Totem, Wolf Totem, Whirling Frenzy) 4/Fighter 2/Disciple of Dispater 8/anything 6 (I'd go Warblade). Take Disciple of Darkness and Power Attack at 1st, Improved Bull Rush at 3rd, Combat Expertise at 5th (fighter bonus), Leap Attack and Shock Trooper at 6th (fighter bonus), and Improved Critical at 9th. You'll kill pretty much everything you touch, no sweat. Alternately, you could go Barb 2/Fighter 4 and fit in an extra feat, if there was something you really wanted. (Knockdown?)