Although it has long since lost a lot of it's impact,
the whole 'bloody banquet' at the end of 2.55 still is a massive kick in the belly - especially seeing everyone sacrifice themselves one by one. It is still my favourite scene of the whole game.
The aftermath of Haurchefant's death of course comes a very close second, especially Edmont's aristocratic stiff-upper-lip finally crumbling and he breaks down sobbing "MYYY SONNN!!!" I admit it, just started sobbing too, weeping to my computer screen "Cry! Cry your manly tears! Grieve for your son!"
And in a similar vein, Ysyale's sacrifice at the gates of Azys Lla.... as much as I disliked her at first, regarding her as a straw activist at best, her selfless attempts to redeem herself for her earlier actions really yanked the heartstrings hard. And of course, turning herself into Shiva and facing down the damn flagship of the Garlean Empire and permanently disabling it's engines even after her death, was an amazing and horrifying sight.