Scarlet's Game Room
I know of 3 creatures that drop Feint. There could be more, I don't have the scoop on ALL the bosses out there yet. I been trying to get Savvy to do my work for me - uh, I mean HELP me, but I haven't had much luck yet.
Barkingham Palace, Marleybone
Black Sun Pyramid Master Chamber, Azteca
Noxious Gas Golem
Main Hall, Marleybone