Gochi
Gochi is the fusion of Goku and Chi-Chi. One day when Gohan was dead (because of Bio-Trunks) a Meta Cooler appeared and attacked Goku and Chi-Chi. Cooler was in his 6th form and Goku could not stop him alone even in his super saiyan 5 stage. Goku needed the extra power, so he fused with Chi-Chi. Now, as Gochi, Cooler was able to be stopped.