Gogeta -the warrior formed by the fusion of Goku  and Vegeta using the fusion dance technique- is by far my favourite fighter in the DBU. This form was first used against Janemba in the Buu saga and later on as a Super Saiyan 4 in Dragon Ball GT against Omega Shenron. Gogeta becomes the most powerful being in the DBU when he is Super Saiyan 4  against Omega Shenron(thats why i like him).