Improved Disarm
Tough choice. I'm really surprised that Cleave is gone, and if I were more objective about it that would probably be my choice. But I'm thinking too much of my bard, whose feats are Combat Expertise, Improved Disarm and Improved Feint, and he's been using all of them, so I'm partial to them. And they're all out. And I still like them.
Of the three, my favourite is Improved Disarm, because of the flavour. Imagine: you're accosted by a bunch of thugs who draw weapons on you. You snatch the rapier out of one enemy's hand and then use that selfsame weapon against its owner or his friends. Boldness to demoralize your attackers!