I like Parappa's "CASH MONEY SON" and Sir Dan's chicken dance.
And Sly's yawn is perfect for using after you get 3 kills with Murray.
I was going to say these two.
Also Heihachiīs laugh is epic and also SIr Danīs: "Bad news.. you lose" taunt --- "Live as if you were to die Tomorrow. Feel like you were to be Reborn now. Face as if you were to Live Forever" FFVII DoC.