When hitting a giant it makes a game.hostile.hurt sound instead of a zombie one, maybe in lower pitch.
This is very annoying especially in resource packs, with changed damage/hit1 sounds.
Since giants are more easy to obtain I think they should be fixed.
As far as my informations go, the Giant is not a supported Mob in the current version of Minecraft. Besides, it's hit sound was always the (now old) player hit sound, which is, as far as I know, not used on any other mob or similar.
I'm going to get that checked before closing though.