Get yourself a Fleshgrinding Harpoon. The two abilities interact... interestingly. Namely, Fleshgrinding gives you a 5-round nearly guaranteed harpooning. After that, the weapon automatically pops back into your hand, ready to annihilate more fools.
1d10 + bonuses damage a round for 5 rounds, which also prevents them from going more than 30ft away from you, halves their speed, and stops them from charging. And, you know, might prevent really weak spellcasters from concentrating on a spell - big whoop.
It sadly becomes easier to remove (you can remove a Fleshgrinding weapon as a Standard action if you make a DC 20 Strength check), but I think they'd still take the damage unless they made that Heal check.
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A Bloodthirsting Fleshgrinding Harpoon would be even nastier:
1) You harpoon a guy, dealing X damage and giving the weapon a blood point.
2) You trigger Fleshgrinding, and let it do its thing. The weapon gets a blood point each turn.
3) The weapon reappears in your hand. You stab someone else, blowing 5 blood points to get a +10 to damage from Bloodthirsting, making it even more likely you'll harpoon them...