I love Spike's default taunt. "YOU'LL NEVER WIN!" I usually use it just after getting killed by someone.
Heihachi's laugh taunt is also amazing. He's just like HAHAHAHAHAHAHAHA. I usually use that if somebody whiffs a super, it's so trolly. --- If I haven't mentioned Trivio in my post, it's because she is so beautiful and precarious that I just wanted to show her how much she means to me.