I'd like to build something using the Falcata that's maybe Rogue-based or some other non-fighter class, and capitalizes on critical hits. Is this possible? Thanks for any advice, even if it's "don't try it, it's a lost cause."
If a Ninja has a vorpal katana and gets a way to extend their crit range with chi, you might match or exceed a fighters critability.
both ninja and rogue work well, you can use rogue talents to pick up some feats as well. The only problem is feats, but if you did a rogue with a Keen falcata you would pretty much be the crit master. throw in a few crit feats and that would work pretty well.
Ranger Two weapon fighting style with kukri's? focus on strength and pick up Power attack feats
or did you mean a non full BAB class?
If so perhaps Inquisitor as the bane ability, ignoring DR on crits at high levels, damage and attack boosts with judgments, wrath spell grants Imp Crit against the target.
If a Ninja has a vorpal katana and gets a way to extend their crit range with chi, you might match or exceed a fighters critability.
Extending crit range doesn't help with vorpal. It still only triggers on a natural 20.
A flurrying monk with a temple sword is probably the easiest and cheapest way to get a high-crit build. You'll only need to enchant one weapon, and you still benefit from the extra attacks. Throwing things is even better, because then you can add rapid shot to the TWF, but I don't think thrown items have much crit range.